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Full text of "Amateur radio : how and why of wireless with complete instructions on operation of receiving outfits"

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BOOK 62 1.384.G76 c. 1 
GRAINGER # AMATEUR RADIO 




3 T153 ODDEnbS 1 



AMATEUR 
RADIO 



AMATEUR RADIO 

How and Why of Wireless with 

Complete Instructions on 

Operation of Receiving 

Outfits 



Maurice J, Grainger 

RadicT Expert, formerly njuith The Westinghouse Electric 
and Mjg Co. and The United States Na<vy 




With over 150 Diagrams 
and Illustrations 



THE JAMES A. McCANN COMPANY 

publishers New York 



Copyright 1922 by 
THE JAMES A. McCANN COMPANY 

All Rights Reserved 

/ 7 £37, 



PRINTED IN THH U. S. A. 



The author wishes to acknowledge his indebtedness to 
the Radio Corporation of America and the Ship 
Owners' Radio Service for much valuable 
material which has been incorporated in 
this book. He also desires to put on 
record his thanks to ]. Her- 
bert Duckworth for edi- ' 
torial advice and 
assistance. 



CONTENTS 



CHAPTER PAGE 

I Radio Waves 1 

How Speech is Carried Without Wires — 
What Wave-Length Is — Speed of Radio 
Waves. 

II Origin of Waves 8 

What Happens at the Transmitter — Re- 
markable Distances Covered with Small 
Amount of Energy — Alternating and High 
Frequency Currents. 

III Magnetism and Electricity ... 13 

Basis of Radio is Magnetism — Phenomena 
of Magnetic Fields and Induction — Sole- 
noids and Bar Magnets. 

IV Head Telephone Receivers ... 18 

Difference Between Land and Radio Head 
Telephone Receivers — The "Rating" of Re- 
ceivers — Ohmic Resistance — Reason for 
Steel Core Electro-Magnets — Why Mica 
Diaphragms are Better than Sheet Iron — 
How to Hook-up Extra Sets of Receivers. 

V How to Make a Simple Crystal Set 25 

(Prepared by U. S. Bureau of Standards) 
Essential Parts of a Receiving Station — 
Antenna, Lightning Switch and Ground 
Connections. 

VI Home-Made Parts for Crystal Re- 
ceiver 34 

A Simple Cardboard Tuner — How to Mount 
Crystals — Some Parts that Can be Impro- 
vised. 



CONTENTS 

CHAPTER PAGE 

VII The Wiring of a Crystal Set . . 42 

Directions for Operating — Uses of Test 
Buzzer — Approximate Cost of Parts of 
Home-Made Crystal Set. 

VIII Vacuum Tubes 48 

T<he V. T. the Keystone of Modern Radio — 
Invented by an Englishman, Perfected by 
an American — Difference Between Two and 
Three-Element Tubes. 

IX Principles of V. T. Transmission . 57 

How Music and the Human Voice are Sent 
Through the Ether by the "Little Bottles"— 
Different Methods of V. T. Transmission. 

X Operation of Tubes 61 

Dangers to be Avoided — Why Filaments of 
Transmitting Tubes Should be Energized 
by Alternating Current — How to Test Tube 
Circuits — Buzzer Modulation. 

XI Aerials 67 

The Functions of Antennae — Hints on Con- 
struction of Aerials — Different Types of 
Aerial— "Skin Effect" on Different Kinds 
of Wire. 

XII Ground Connections 78 

Common Faults of Aerials — How to Put a 
Metal Roof to Use — Proper Place for the 
Lead-in — Uses oLthe Counterpoise. 

XIII Static 84 

Nature's Own Transmitter — The Action of 
Lightning on Receiving Sets. 

XIV The Armstrong Feed-Back Circuit . 87 

Regenerative Circuit Most Revolutionary 
Contribution to Wireless Art — The Discov- 
ery One of the Romances of Radio — How 
It Made Modern Broadcasting Possible. 



CONTENTS 



CHAPTER 

XV 



XVII 



XVIII 



XIX 



Some Hook-Ups 

A Simple Long^ Wave Receiver — Self- 
Heterodyne Circuits — Short Wave Regen- 
erative Receivers — A Hook-up Without an 
Aerial. 



PAGE 

92 



XVI The Newest Circuits 



100 



The Loose Coupler, the Variometer and the 
Vario-Coupler — Honeycomb Coils — The 
Shielding of Panels. 



Audio and Radio Frequency Ampli- 
cation 113 

Difference Between "A.FA." and "R.F.A" 
— The Uses of Each. 

Condensers 123 

How Condensers Assist in Tuning — Fixed 
and Variable Condensers. 

Tuning and Interference . . . 127 

Proper Method of Operation of Audion 
Set — How to Avoid Interference, or QRM 
— Way to Find the Desired Wave-Length — 
Meaning of Resonance Between Transmitter 
and Receiver. 



XX A Personal Experience .... 136 

How a First Step of Amplification Acted as 
a Detector, and the Second Step as a One- 
Step Amplifier and Oscillator — Visiting the 
"Other Fellow's" Station. 

XXI Storage Batteries 141 

Accumulators Necessary for Radio Receiv- 
ers — How Batteries are Rated — Testing and 
Charging Batteries. 

Radio Glossary 146 

U. S. Radio Laws and Regulations . 154 



LIST OF ILLUSTRATIONS 

Principle of Wave Transmission 3 

Wave Curves # . 9 

Direction of Current Flow 15 

Telephone Receiver 20 

Antenna 27 

Radio Set Installed in House 32 

Home Made Parts for Crystal Receiver 33 

Upright Panel and Base 39 

Diagram of Audion Tube 53 

Diagrams of Aerials 68, 70, 72, 74, 75, 77 

Circuit Used for Transatlantic Tests 88 

Hook-Ups .... 93, 96, 98, 101, 103, 105, 107, 109, 110, 111 

Radio Symbols 114, 115, 116, 117 118 

Connection for Receiver Using Loop Aerial 121 

Diagram Showing Contractions of Fixed Condensers 124 

Variable Condenser 124 

Reducing "Hum" from Nearby Power Lines 127 

Map Showing Broadcasting Stations 132 

Map of Stations Received at Scotland 134 

Arlington Weather Reports 150 

Arlington Time Signals .••..._._ 151 

International Morse Code 155 



INTRODUCTION 

THIS book has been compiled especially for 
the amateur owner of a radiophone receiver 
who knows little, or nothing, about why and 
how his instrument works. Many of those 
who have acquired radio sets are not satisfied 
with simply turning knobs, finding sensitive 
spots on crystals, regulating the amount of in- 
candescence in their vacuum tubes, and then 
sitting calmly back to enjoy the broadcasted 
programs. 

They have become fascinated by the ro- 
mance of radio; they want to learn something 
of the inner workings of this new and won- 
derful scientific toy; they want explained to 
them in language that even a layman may un- 
derstand, something of the mysteries of this 
seemingly most inexplicable and uncanny of 
contraptions that even a child can operate. 
Such words as "dielectrics," "series multiple- 
circuits," "heterodyne" and "rheostats" frank- 
ly puzzle him. He wants made as plain to 
him as the action of a typewriter, or camera, 



INTRODUCTION 

just why sounds sent out from a broadcasting 
station many miles away can be picked up 
with a jumble of wire, crystals and electric 
bulbs. 

It is to satisfy the curiosity— reasonable and 
commendable curiosity — of this large and 
growing class of radio enthusiasts that this 
work has been put together. In reality there 
are few subjects that can be so readily under- 
stood as "wireless." To the "old-timers" and 
the real "ham" of the wireless game, and to 
others who have made a study of matters elec- 
trical this book is not primarily addressed. 
But even the amateur who has been through 
the hard but interesting school of practical ex- 
perimentation — the school that started before 
the war with the "plain aerial spark trans- 
mitter," will, I think, find many things of 
value between these covers. 

To those whose knowledge of things elec- 
trical is, to say the least, very scant, but who 
will never be satisfied until they can conscien- 
tiously tell themselves that they at least com- 
prehend the fundamental principles upon 
which this most marvellous of inventions is 
based, this book is particularly and respect- 
fully dedicated. 

The Author. 



AMATEUR 
RADIO 



CHAPTER I 



RADIO WAVES 



How Speech is Carried Without Wires — What Wave- 
Length Is — Speed of Radio Waves 

How does a radiophone work? How is 
speech carried without wires? How do num- 
berless receiving sets pick up the messages or 
music from the same broadcasting station? 
Questions like these puzzle many people who 
have only recently, through the radiophone, 
become interested in matters electrical. 

By the use of a little analogy I will try to 
make clear just how the human voice and 
music are sent radiating out into the night air 
and are picked up from places at all points 
of the compass. 

Imagine that a small pebble has been 
thrown into a big pond. Tiny ripples com- 
mence to circle out from the point of con- 
tact. Next a good sized brick has been cast 
into the water. Instead of ripples miniature 
waves are set rolling in ever-widening circles. 



2 AMATEUR RADIO 

Perhaps the wavelets, both the big ones and 
the smaller fellows, meet a reed or some other 
obstacle sticking out of the water. Where the 
ripples hit the obstruction they are momenta- 
rily bent. But they proceed on their way just 
the same. 

Now you can liken the missive thrown into 
the water to the transmitter. The sticks 
showing above the surface of the water are 
the receiving stations. The rock is like the 
powerful broadcaster; the pebble a small 
station. (See Fig. i.) 

Tall buildings, trees and other obstructions, 
absorb some of the power of the ether waves 
just as obstructions met with on the surface of 
the pond weaken, to some extent, the force of 
the water waves that strike them. 

Radio waves are like these commotions set 
up on the surface of a pond. Just as ***£ wa- 
ter waves are so many inches apart so are the 
.ether waves. Ether waves are measured in 
meters. When you say that the wave is 360 
^meters long you mean that measured from 
crest to crest the wave is that many meters in 
length. 

But while waves set up on a lake will grad- 
ually die out until they completely disappear, 
the scientists have a theory that ether waves^ 











i- 

i 



% 



Fig. 1 
Principle of wave transmission pictorially shov/n. A. Transmitting sta- 
tion. B and C Receiving stations. 



4 AMATEUR RADIO 

never cease to exist when they are once ret in 
motion. They go on travelling into space for 
ever. Were there receivers sensitive enough 
to detect them they would be picked up thou- 
sands of years after they had been set free arid 
trillions of miles away from the transmitter, 
for ether waves move at the rate of 186,000 
miles a second. 

Now let me attempt to visualize for the 
reader just how these "wave-lengths" are uti- 
lized in the operation of wireless telegraphy 
and telephony. I am indebted to the Ship 
Owners' Radio Service, Inc., for the follow- 
ing exceedingly clear and interesting explana- 
tion of how the different wave-lengths are 
prevented from interfering with each other : 

We might compare four radio transmitting 
stations to four singers on a single stage. As 
long as the quartet sang togetH r everything 
would be fine. But suppose that the tenor 
sang "Home Sweet Home," the soprano, 
"Bubbles," the basso, "Annie Laurie" and the 
contralto, "The Star Spangled Banner" all at 
the same time. The result would be what, in 
radio parlance, is referred to as "interference." 

Now suppose that you had in your pocket 
a little device that, when placed against your 
ears and properly adjusted, would exclude the 



^MATEUR RADIO 5 

basso, contralto, and tenor voices, but would 
allow the soprano voice to pass. The result 
w r ould be that you would hear only the clear 
soprano strains of "Bubbles," unmarred by the 
bedlam of "Annie Laurie," "Home Sweet 
Home," and "The Star Spangled Banner." 
You would simply turn the knob on your little 
device so that it would exclude the basso, tenor, 
and soprano, but pass the contralto voice, and 
you would hear your favorite song, undis- 
turbed by the soprano "Bubbles," or any other. 

If the singers were compared to radio sta- 
tions, and you called the basso voice a "200- 
meter wave length," the tenor a "600-meter 
wave length," the contralto a "360-meter wave 
length," and the soprano a "1200-meter wave 
length," and your little pocket device you 
compared to a radio receiver, the analogy 
would be complete. 

In order that a number of radio stations in 
the same vicinity may transmit signals at the 
same time, and not interfere with one another, 
one will transmit on a 200-meter wave length, 
another on 360 meters, another on 600 meters, 
another on 1200 meters, and so on. In order 
that a radio receiving station may listen to 
any station at will, the receiving instrument 
is provided with one or more adjusting knobs 



6 AMATEUR RADIO 

or switches, so that the "wave-length" of the 
receiver may be adjusted to correspond with 
the wave-length of the station it is desired to 
hear. This process is known as "tuning." 

The wave-length range has no direct bear- 
ing on the distance over which a sending sta- 
tion may be heard. This depends on the 
power used by the transmitting station, and 
the sensitiveness of the receiving instrument, 
just as in the theatre analogy, a partially deaf 
man in the front row could not hear as well 
as the man in the back row who had good 
hearing. If the partially deaf man went to 
the back row, he might not hear at all unless 
the singer fairly shouted. The loudness of 
the singing would compare with the "power" 
of a transmitting station, and the degree of 
deafness would compare with the sensitive- 
ness of a receiver. 

To carry the theatre analogy one step far- 
ther, suppose that one man in the audience 
sat directly behind a large pillar. He would 
probably not hear the singing as well as the 
man' who sat in the open. Tall steel build- 
ings, abrupt hills, etc., obstruct radio signals 
in a somewhat similar manner, and that is why 
the amateur who lives among skyscrapers will 
not get quite as good results as the amateur 



AMATEUR RADIO 7 

who lives among two or three-story buildings, 
or, better still, out in the country. 

The term "wave-length range," as I have 
said, has nothing to do with the range in miles. 
Wave-length is simple to understand. Mes- 
sages from the transmission stations are sent in 
the form of waves of electrical energy. The 
actual length of these waves may vary from 
160 to 26,000 meters. To receive a broad- 
casting station which you know transmits on 
a wave-length of 360 meters, you simply tune 
your receiver to 360 meters. You should 
then receive only that one station. To receive 
stations sending on a longer or shorter wave- 
length, adjust your receiver accordingly. 
Every receiving instrument has a certain 
wave-length-range, which means that it re- 
sponds to all wave-lengths within these limits, 
provided, of course, the transmitting stations 
are within the range in miles of the receiving 
apparatus. The different wave-lengths make 
it possible to send different messages at the 
same time without undue confusion. 

The range in miles depends on the power 
of the transmitting station, the sensitiveness of 
the receiver, and local conditions. This 
makes it impossible to specify the exact range 
in miles of any particular outfit. 



CHAPTER II 

ORIGIN OF WAVES 

What Happens at the Transmitter — Remarkable Distances 
Covered with Small Amount of Energy — Alter- 
nating and High Frequency Currents 

WHAT sets radio "waves" in motion? A 
series of vibrations in the ether is set up when- 
ever a flow of electricity takes place. The 
small particles from which electricity is com^- 
posed, called electrons, theoretically have a 
hold on the ether, so to speak, and cause a vi- 
bration, or strain, to be set up in the ether 
whenever a movement of electricity takes 
place. (See Fig. 2.) 

The smallest ether disturbance, even that 
caused by the flow of current when ringing a 
bell, sets up ether waves which travel an un- 
known distance. The real problem is not how 
transmitting sets may be improved, but how 
receiving sets may. Ether waves can be pro- 
jected around the earth with an expenditure 

of very little energy. At present our trans- 

8 



SENDING 
KE1Y 




«HMMO 

Hook-up of Simplest Type of Transmitting Set, 




^ V^ A^<~ ^ ^ /^, ^ 

4 A/IMAA^A^Vnaaaaaa/ 



Fig. 2 — Wave Curves 
(1) Continuous Oscillations. (2) Word Sound Waves. 
(3) Sound Waves Carried by Oscillations. (4) Continuous 
Wave Train. (5) Wave Train Carrying Speech. (6) Re- 
ceived Speech. 



io AMATEUR RADIO 

oceanic stations use hundreds of kilowatts of 
power because receiving apparatus w T ill not 
detect signals if less power be used. 

Ether waves, as I have already pointed out, 
travel at a speed of 186,000 miles a second. 
This is about 300,000,000 meters per second. 
Since the speed of ether waves, or vibrations, 
is nearly the same under all conditions it fol- 
lows that if we know the wave-length a trans- 
mitting station is using we can tell how many 
waves or vibrations there are per second, or, 
in other w r ords, the frequency. 

The present practical wave-length limits for 
radio telegraphy and telephony are between 
100 meters and 20,000 meters, which repre- 
sents a frequency range of from about 2,000,- 
000 to 15,000 a second which, of course, would 
be inaudible, as the normal human ear does 
not respond to sound waves below forty nor 
above 10,000 vibrations per second. There- 
fore radio frequencies, as they are called, 
cannot be heard. 

We must then reduce the radio frequencies 
to audible or audio frequencies so that they 
can be heard. This is performed by the de- 
tector in the receiving apparatus. This de- 
tector changes high frequency radio current 



Frequency and Wave Length Tables 

W. L. — Wave Lengths in Meters. F. — Number of Oscillations per Second. 
O. or V L C is called Oscillation Constant. C. — Capacity in Micro Farads. 
L* — Inductance in Centimeters. 1000 Centimeters = 1 Microhenry. 



W.L. 
50 

100 

150 

200 

250 

800 

850 

400 

450 

500 

550 

600 

700 

800 

900 

1000 

1100 

1200 

1800 

1400 

1500 

1600 

1700 

1800 

1900 

2000 

2100 

2200 

2300 

2400 

2500' 

2600 

2700 

2800 

2900 

sooo 

4000 
6000 
6000 
7000 
8000 
9000 

loooo 

11000 
12000 
1ZQG0 
14000 
15000 
16000 



6,000,000 

3,000,000 

2,000,000 

1,500,000 

1,200,000 

1,000,000 

857,100 

750,000 

666,700 

600,000 

545,400 

500,000 

428,600 

875,000 

333^00 

800,000 

272,730 

250,000 

230,760 

.214,380 

200,000 

187,500 

176,460 

J 66,670 

157,890 

150,000 

142^50 

136,350 

130,430 

125,000 

120,000 

IISJUO 

111,110 

107440 

103,450 

100,000 

<75,000 

60,000 

50,000 

41,300 

87,500 

80,000 
27,300 
25,000 
23400 
21,400 
20,000 
IS ; 750 



O. or VL.C. 


L.C. 


.839 


.7039 


1.68 


2.82 


2.52 


6.35 


ajf 


11.29 


4.19. 


17.55 


5.05 


25.30 


5.87 


34.46 


6.71 


45.03 


7.55 


57.00 


8.39 


70.39 


9.23 


85.19 


10.07 


101.41 


11.74 


137.83 


13.42 


180.10 


15.10 


228.01 


16,78 


281.57 


18.45 


340.40 


20.13 


405.20 


21.81 


475.70 


23.49 


551.80 


25.17 


633.50 


26,84 


720.40 


28.52 


813.40 


30.20 


912.00 


81.88 


1016.40 


83.55 


1125.60 


85.23 


1241.20 


86.91 


1362.40 


88.59 


1489.30 


40.27 


1621.80 


41.95 


1759.70 


43.62 


1902.60 


45.30 


2052.00 


46.69 " 


2207.00 


48.06 


236S.30 


50.33 


2533.20 


67 J 1 


4504.00 


83.89 


7028.00 


100.7 


10130.00 


117.8 


13630.00 


134.1 


18000.00 


;1S10 


22820.00 


167*.9 


28150.00 


184.8 


84150.00 


201.5 


40600.00 


218.3 


47600.00 


235.0 


55200.00 


252.0 


68500.00 


269.0 


72800.00 



12 AMATEUR RADIO 

to a pulsating direct current which actuates 
the telephone receivers. 

Ether waves when they strike the aerial are 
alternating, that is, flow in two directions — 
strike down to the earth through the antenna 
and ground connection, and return through 
the earth to the transmitter, thousands of 
miles away as is sometimes the case. The next 
vibration, or wave, flows in the opposite direc- 
tion — through. the earth to the ground connec- 
tion, up through the receiving set and out of 
the aerial. These two operations are called 
a "cycle." The current travels with the speed 
of light. 

As there are many million vibrations per 
second I will leave it to the reader to imagine 
how many of these cycles occur in say ten min- 
utes of receiving — or in other words how 
many billions or trillions of times the current 
changes its direction during the ten minutes. 



CHAPTER III 



MAGNETISM AND ELECTRICITY 

Basis of Radio is Magnetism — Phenomena of Magnetic 
Fields and Induction — Solenoids and Bar Magnets 



To understand the operation of radio it is 
absolutely necessary to be equipped, at least, 
with a knowledge of the elementary principles 
of electricity. Let me plunge right into this 
subject: 

If a fragment of hard steel be brought 
within the influence of a permanent magnet 
it acquires and retains a certain amount of 
magnetism. By stroking the magnet with the 
hard steel the amount of magnetism held is 
greatly increased. Actually, the steel bar be- 
comes almost as powerful as the magnet from 
which it obtained its magnetism. The piece 
of hard steel is then known as a permanent 
magnet also because, unless it is subjected to 
heating or pounding, it holds its magnetism 
indefinitely. 

When you bring a piece of soft iron in close 

proximity to a permanent magnet it also be- 

13 



i 4 AMATEUR RADIO 

comes a magnet and will attract other smaller 
pieces of iron, but as soon as the permanent 
magnet is taken away the soft iron loses almost 
all its magnetism. So soft iron can only form 
a temporary magnet. 

If a rod of iron or steel be wound with a 
number of turns of wire, and a current passed 
through the wire the rod becomes magnetized, 
one end being called the north pole and the 
other the south pole, (See Fig. 3). When 
the bar is of iron and the current is cut off it 
loses its magnetism instantly; if it is of steel 
the rod is made a permanent magnet. 

It is known that any wire carrying current 
has a small magnetic field around it, the mag- 
netic field varying according to the strength 
of the current. The extent of this magnetic 
field is shown in Fig. 4. 

If the direction of the current in the wire 
be reversed the direction of the magnetic field 
is reversed, or, as it is called, the "polarity" 
is reversed. If the current be passed through 
the wire from A to B the lines of force around 
the wire will revolve clockwise, or left to 
right. If the current be passed through in 
the opposite direction, from B to A, then the 
lines of force will flow in the other direction, 
or counter clockwise. (See Fig. 5.) 



A "DOQDS 



) B 



OIRECTION OF CURRENT FLOW 

Fig. 3 

^DIRECTION OF CURRENT FLOW 



Ad 



<H 



» \/ 



k> 





3 B 



Fig. 4 




N 



Fig. 5 



16 AMATEUR RADIO 

In direct current (D.C.) the electricity 
flows in one direction, and the lines of force 
move in one direction. In alternating cur- 
rent (A.C.) or in current that changes its di- 
rection a certain number of times a second, 
the lines of force change their direction twice 
as often per second. If it were a sixty cycle 
current, then the lines of force would change 
their direction 120 times, for there are two 
changes of direction in each cycle. 

By winding a copper wire in the shape of a 
coil and passing a current through it, the coil 
acquires the properties of a magnet. As cop- 
per is non-magnetic it is very easily seen that 
as soon as the current is shut off the magnetism 
disappears. This is known as a solenoid. By 
inserting a sof* iron core in the hollow of the 
solenoid the magnetic lines of force, because 
of the much higher magnetic properties of 
iron as compared with air, are greatly in- 
creased. This also increases what is known 
as self-induction. 

If a bar magnet be passed through a coil of 
wire carrying no current it will put current 
into the wire. This is self-induction. With- 
draw the magnet and the current in the wire 
disappears. 

If a coil of wire carrying current be placed 



AMATEUR RADIO 17 

close to another coil of wire not carrying cur- 
rent it will induce a current in the latter. In 
all these cases the induced current in the coil 
is due to the change in the number of lines 
of magnetic force through the coil. 

It is very important that you should know 
something of magnetism and induction be- 
cause it will help you to understand the func- 
tions of almost every part of your receiver. 

For instance, there are the head telephones. 
You could not understand why the ether waves 
are made audible in the headpiece unless 
you had it clear in your mind just what 
magnetism is. 



CHAPTER IV 

HEAD TELEPHONE RECEIVERS 

Difference Between Land and Radio Head Telephone Re- 
ceivers — The "Rating" of Receivers — Ohmic Resistance 
— Reason for Steel Core Electro-Magnets — Why 
Mica Diaphragms are Better than Sheet Iron — 
How to Hook-up Extra Sets of Receivers 

The telephone receiver as used in wireless 
telegraphy and telephony is practically the 
same type as that used on land telephone lines, 
but as they must respond to extremely weak 
currents they' are made with very light dia- 
phragms and are wound with a great many 
turns of fine wire. 

In the telephone receiver are usually two 
electro-magnets having steel cores, or per- 
manent magnets. These magnets are wound 
with many turns of fine insulated wire, the ef- 
fect being a solenoid with a steel core. The 
reason for the steel core, which may seem to 
contradict what was written in the last chap- 
ter, is that owing to the very small amount 

of current that comes into the receivers, via the 

18 



AMATEUR RADIO 19 

aerial, tuner and detector, it is insufficient to 
make magnets of a soft iron core and move the 
diaphragm of the receiver. Manufacturers, 
accordingly, make the cores permanent mag- 
nets by making them of steel, thus always ex- 
erting a pull on the metal diaphragm, but not 
enough to pull it to the magnets. (See 
Fig. 6.) 

When the feeble radio current arrives at 
the telephone all the energy is used in mag- 
nifying the attraction that the magnet exerts 
on the diaphragm. This diaphragm is an ex- 
ceedingly sensitive piece of the 'phone 
mechanism. It takes very little energy to 
move it. 

Telephone receivers will not work with al- 
ternating current. The current moving in 
one direction would neutralize the current 
moving in the opposite direction and there 
would be no vibration of the diaphragm. 
Therefore the ether waves, which are alternat- 
ing currents, must be changed to pulsating di- 
rect current. This is done either by means of 
a crystal or audion detector. 

The average beginner regards a pair of re- 
ceivers as a couple of metallic boxes with hard 
rubber ear caps. Receivers all look more or 
less alike, but there is a vast difference on the 




Fig. 6 
Fig. 6 — Diagram of Telephone Receiver, Showing the Positions 
of the Diaphragm at Different Stages of Magnetic Saturation. 
A. Shows Normal Position of the Diaphragm. B. Shows Posi- 
tion of Diaphragm When it is Attracted to the Magnet by the 
Incoming Signals. C. Shows Position of Diaphragm When 
it Springs Back at the End of the Oscillation, 



AMATEUR RADIO 21 

inside. A receiver to really work right should 
be wound with very fine copper wire, as the 
whole theory of the radio receiver hinges on 
the fact that there must be a great many turns 
of wire very close to an iron core. 

While receivers are rated by the resistance 
that they have, this method of classifying them 
is entirely wrong. As stated above, the re- 
ceiver must have these turns of fine wire about 
the pole pieces of the magnets, and in order 
to get this a great quantity of wire has to be 
used. The easiest way to rate the receiver is 
by the resistance that this wire has, which is 
really wrong, as the resistance is really a det- 
riment to the 'phones. 

The whole idea is to get the number of 
turns with the least resistance. In order to 
reduce this resistance a larger size wire may 
be used, but just as soon as this is done it will 
be found that owing to the thickness of the 
wire the distance from the poles will rapidly 
increase, thereby lowering the efficiency of 
the receiver. 

In order to have a receiver that will give 
a high ohmic reading or resistance, some man- 
ufacturers have gone so far as to wind the re- 
ceivers with German silver wire. As this 



22 AMATEUR RADIO 

wire has a high resistance, it will be seen that 
the receivers will show a high resistance. 

This theory is absolutely contrary to correct 
receiver design, as the receiver has the resist- 
ance all right, yet the number of turns is de- 
creased and actually less wire is used. Even 
the beginner at the game can readily under- 
stand that this will make the receiver less effi- 
cient, as the high resistance of the 'phone will 
actually deaden the signals, and, owing to the 
fact that there are not as many turns, the re- 
ceiver will be far less efficient. 

Another thing in a receiver that may be 
greatly improved upon is the diaphragm. 
This is usually a piece of thin sheet iron, and 
it is the vibrations of iron that are actually 
heard. While it may do very well for cheap 
receivers to use this iron diaphragm, the best 
receivers- on the market use a diaphragm of 
some other material that is more pliable and 
can be deflected to a greater degree. This 
will bring the signals in louder, as with the 
iron diaphragm the magnets have to be placed 
so close to the diaphragm that they will hit 
each other and cause the signals to be dis- 
torted. 

Of course this only happens with very loud 
signals. With the other type of diaphragm 



AMATEUR RADIO 23 

some sort of material, such as mica, may be 
used, and as it is far more flexible it will be 
found that far greater motion is secured. 
This is done by attaching a small piece of 
steel to the mica and the steel is what pulls 
the diaphragm to the magnets. Thus it will 
be seen that while steel is still used, the deflec- 
tion of the mica will give much better results. 

It is well to remember that with a pair of 
'phones care must be taken not to short cir- 
cuit the storage battery through them, as the 
heat generated will cause the fine wire to melt 
very quickly, and make the receivers worthless 
because there will not be a complete circuit. 

Another thing to avoid is dropping the re- 
ceivers. This is very apt to break the hard 
rubber ear-caps, and will also tend to demag- 
netize the magnets. If a pair of receivers 
once get in this condition the best thing to do 
is to throw them away. 

Do not attempt to rewind a receiver, as very 
fine wire is used for this purpose, and it is 
very apt to be broken while winding, and 
never be discovered until after all the wire is 
in place. It is also practically impossible to 
make a radio receiver out of an ordinary tele- 
phone receiver. These receivers are not built 
right for this sort of work, and the beginner 



24 AMATEUR RADIO 

is cautioned not to waste time experimenting 
with them. 

Some amateurs desire to use more than one 
pair of receivers, so that more than one per- 
son may listen in at the same time, yet they 
are puzzled as to how to connect the receivers 
up. This is very simple, as the sets are con- 
nected in series. That is, the end of one re- 
ceiver cord is connected to the radio set in 
the usual place, and the other terminal is con- 
nected to the terminal of the next pair of re- 
ceivers, the remaining receiver cord being 
connected back to the set to the other binding 
post of the radio set. Any number of re- 
ceivers may be connected on in this way. 



CHAPTER V 

HOW TO MAKE A SIMPLE CRYSTAL SET 

(Prepared by U. S. Bureau of Standards) 

Essential Parts of a Receiving Station — Antenna, Light- 
ning Switch and Ground Connections 

THIS article tells how to construct the entire 
receiving station, including antenna as well as 
a crystal-detector receiving set. This station 
will enable one to hear the messages sent from 
medium-power transmitting stations within an 
area about the size of a large city, and to hear 
high-power stations within fifty miles, pro- 
vided the waves used by those stations have 
wave frequencies between 500 and 1500 kilo- 
cycles per second (i. e., wave lengths between 
600 and 200 meters). Much greater dis- 
tances are often covered, especially at night. 
If the amateur constructs the coil and other 
parts as indicated, the total cost of this set can 
be kept down to about $6.00. If, however, a 
specially efficient outfit is desired, the cost may 

be about $15.00. 

25 



26 AMATEUR RADIO 

There are five essential parts to a receiving 
station : the antenna, lightning switch, ground 
connections, receiving set, and phone. The 
received signals come into the receiving set 
through the antenna and ground connection. 
In the receiving set they are converted into an 
electric current which produces the sound in 
the "phone." The phone is either one or a 
pair of telephone receivers worn on the head 
of the listener. 

The purpose of the lightning switch is to 
protect the receiving set from damage by 
lightning. It is used to connect the antenna 
directly to ground when the receiving station 
is not being used. When the antenna and the 
connection to the ground are properly made 
and the lightning switch is closed, an antenna 
acts as a lightning rod and is a protection, 
rather than a source of danger to the building. 

The principal part of the station is the "re- 
ceiving set." In the set here described it is 
subdivided into two parts, the "tuner" and the 
"detector," and in more complicated sets still 
other elements are added. 

The antenna is simply a wire suspended be- 
tween two elevated points. Wherever there 
are two buildings, or a house and a tree, or 
two trees with one of them very close to the 



28 AMATEUR RADIO 

house, it relieves one of the need of erecting 
one or both antenna supports. The antenna 
should not be less than 30 feet above the 
ground and its length should be between 75 
and 100 feet. (See Fig. 7.) While this 
figure indicates a horizontal antenna, it is not 
important that it be strictly horizontal. It is 
in fact desirable to have the far end as high as 
possible. The "lead-in" wire or drop-wire 
from the antenna itself should run as directly 
as possible to the lightning switch. If the 
position of the adjoining buildings or trees is 
such that the distance between them is greater 
than about 125 feet, the antenna can still be 
held to a 100 feet distance between the insu- 
lators by increasing the length of the piece of 
rope (D) to which the far end of the antenna 
is attached. The rope (H) tying the antenna 
insulator to the house should not be lengthened 
to overcome this difficulty, because by so do- 
ing the antenna "lead-in" or drop-wire (J) 
would be lengthened. 

Details of Parts — The parts will be men- 
tioned here by reference to the letters appear- 
ing in Figs. 7, 8, 9. 

A and I are screw eyes sufficiently strong to 
anchor the antenna at the ends. 

B and H are pieces of rope }i or ]/ 2 inch in 



AMATEUR RADIO 29 

diameter, just long enough to allow the an- 
tenna to swing clear of the two supports. 

D is a piece of ^ or ^ inch rope suffi- 
ciently long to make the distance between E 
and G about 100 feet. 

C is a single-block pulley which may be 
used if readily available. 

E and G are two insulators which may be 
constructed of any dry hard wood of sufficient 
strength to withstand the strain of the an- 
tenna; blocks about 1^x2x10 inches will 
serve. The holes should be drilled as shown 
in Fig. 7 sufficiently far from the ends to 
give proper strength. If wood is used the in- 
sulators should be boiled in paraffin for about 
11 hour. If porcelain wiring cleats are avail- 
able they may be substituted instead of the 
wood insulators. If any unglazed porcelain 
is used as insulators, it should be boiled in 
paraffin the same as the wood. Regular an- 
tenna insulators are advertised on the market, 
but the two improvised types just mentioned 
will be satisfactory for an amateur receiving 
antenna. 

F is the antenna about 100 feet between the 
insulators E and G. The wire may be No. 
14 or 16 copper wire either bare or insulated. 
The end of the antenna farthest from the re- 



30 AMATEUR RADIO 

ceiving set may be secured to the insulator 
(E) by any satisfactory method, being care- 
ful not to kink the wire. Draw the other end 
of the antenna wire through the other insu- 
lator (G) to a point where the two insulators 
are separated by about ioo feet, twist the 
insulator (G) so as to form an anchor as 
shown in Fig. 7. The remainder of the an- 
tenna wire (J) which now constitutes the 
"lead-in" or drop-wire should be just long 
enough to reach the lightning switch. 

K is the lightning switch. For the purpose 
of a small antenna this switch may be the 
ordinary porcelain-base, 30 ampere, single- 
pole double-throw battery switch. *These 
switches as ordinarily available, have a porce- 
lain base about 1 by 4 in. The "lead-in" wire 
(J) is attached to this switch at the middle 
point. The switch blade should always be 
thrown to the lower clip when the receiving 
set is not actually being used and to the upper 
clip when it is desired to receive signals. 

L is the ground wire for the lightning 
switch; it may be a piece of the same size 
wire as used in the antenna, of sufficient length 
to reach from the lower clip of the lightning 
switch (K) to the clamp on the ground rod 
(M). 



AMATEUR RADIO 31 

M is a piece of iron pipe or rod driven 3 
to 6 feet into the ground, preferably where 
the ground is moist, and extending a sufficient 
distance above the ground in order that the 
ground clamp may be fastened to it. Scrape 
the rust or paint from the pipe before driving 
in the ground. 

N is a wire leading from the upper clip 
of the lightning switch through the porce- 
lain tube (O) to the receiving set binding 
post marked "antenna." 

O is a porcelain tube of sufficient length 
to reach through the window casing or wall. 
This tube should be mounted in the casing or 
wall so that it slopes down toward the out- 
side of the building. This is done to keep the 
rain from following the tube through the wall 
to the interior. 

Fig. 8 shows the radio receiving set in- 
stalled in some part of the house. 

P is the receiving set which is described in 
detail below. 

N is the wire leading from the "antenna" 
binding post of the receiving set through the 
porcelain tube to the upper clip of the light- 
ning switch. This w r ire, as w r ell as the wire 
shown by Q, should be insulated and prefer- 
ably flexible. A piece of ordinary lamp cord 




Fig. 8 



AMATEUR RADIO 33 

might be unbraided and serve for these two 
leads. 

Q is a piece of flexible wire leading 
from the receiving set binding post marked 
"ground" to a water pipe, heating system or 
some other metallic conductor to ground, ex- 
cept M, Fig. 8. If there are no water pipes 
or radiators in the room in which the receiv- 
ing set is located, the wire should be run out 
of doors and connected to a special "grouad" 
below the window, which shall not be the 
same as the "ground" for the lightning switch. 
It is essential that for the best operation of 
the receiving set this "ground" be of the very 
best type. If the soil near the house is dry 
it is necessary to drive one or more pipes or 
rods sufficiently deep to encounter moist earth 
and connect the ground wire to the pipes or 
rods. This distance will ordinarily not ex- 
ceed 6 feet. Where clay soil is encountered 
this distance may be reduced to 3 feet, while 
in sandy soil it may be increased to 10 feet. 
If some other metallic conductor, such as the 
casing of a drilled well, is not far away from 
the window, it will be a satisfactory "ground." 



CHAPTER VI 



HOME-MADE PARTS FOR CRYSTAL RECEIVER 

A Simple Cardboard Tuner — How to Mount Crystals- 
Some Parts that Can be Improvised 



The detector and phone will have to be 
purchased. The tuner and certain accessories 
can be made at home. 

Tuner (R, Fig. g) — This is a piece of 
cardboard or other non-metallic tubing with 
turns of copper wire wound around it. The 
cardboard tubing may be an oatmeal box. Its 
construction is described in detail below. 

Crystal Detector (S, Fig. q) — The con- 
struction of a crystal detector may be of very 
simple design and quite satisfactory. The 
crystal, as it is ordinarily purchased, may be 
unmounted or mounted in a little block of 
metal. For mechanical reasons the mounted 
type may be more satisfactory, but that is of 
no great consequence. It is very important, 
however, that a very good tested crystal be 
used. It is probable also that a galena crystal 
will be more satisfactory to the beginner. 

34 




v= ' 




SW 



^ 



.GROUND 



® 

TUNLR 




JO 9 8 7 6 S A 3 2 1 



'■l-TURNTOEACHTAP 



I SIS [7 



lO-flJRNS I 
TOZMhTAP 



zz 




TWI5TEDTAP 



\l 



6Q9P4 




TELLPHONL Rf£IIV£P^ 



Fig. 9 



36 AMATEUR RADIO 

The crystal detector may be made up of a 
tested crystal, three wood screws, short piece 
of copper wire, a nail, set-screw type of bind- 
ing post, and a wood knob or cork. The 
tested crystal is held in position on the wood 
base by three brass wood-screws as shown at 
i, Fig. 9. A bare copper wire may be 
wrapped tightly around the three brass screws 
for contact. The assembling of the rest of the 
crystal detector is quite clearly shown in 
Fig. 10. 

Phone (T , Fig. q) — It is desirable to use 
a pair of telephone receivers connected by a 
head band, usually called a double telephone 
headset. The telephone receivers may be any 
of the standard commercial makes having a 
resistance of between 2000 and 3000 ohms. 
The double telephone receivers will cost more 
than all the other parts of the station com- 
bined, but it is desirable to get them, espe- 
cially if one plans to improve his receiving 
set later. If one does not care to invest in a 
set of double telephone receivers, a single tele- 
phone receiver with a head band may be used; 
it gives results somewhat less satisfactory. 

Accessories — Under the heading of acces- 
sory equipment may be listed binding posts, 
switch arms, switch contacts, test-buzzer, dry 



AMATEUR RADIO 37 

battery, and boards on which to mount the 
complete apparatus. The binding posts, 
switch arms and switch contacts may all be 
purchased from dealers who handle such 
goods or they may be quite readily improvised 
at home. There is nothing peculiar about the 
pieces of w r ood on which the equipment is 
mounted. They may be obtained from a dry 
packing-box and covered with paraffin to 
keep out moisture. 

The following is a detailed description of 
the method of winding the coil, construction 
of the wood panels, and mounting and wiring 
the apparatus: 

Tuner — See R, Fig 9. Having supplied 
oneself with a piece of cardboard tubing 4 
inches in diameter and about ]/ 2 pound of 
No. 24 (or No. 26) double cotton covered 
copper wire, one is ready to start the winding 
of the tuner. Punch two holes in the tube 
about y 2 inch from one end as shown at 2 on 
Fig. 9. Weave the wire through these holes 
in such a way that the end of the wire will 
be quite firmly anchored, leaving about 12 
inches of the wire free for connections. Start 
with the remainder of the wire to wrap the 
several turns in a single layer about the tube, 
tightly and closely together. After 10 com- 



38 AMATEUR RADIO 

plete turns have been wound on the tube hold 
those turns snugly while a tap is being taken 
off. This tap is made by making a 6 inch 
loop of the wire and twisting it together at 
such a place that it will be slightly staggered 
from the first tap. This method of taking off 
taps is shown quite clearly at U, Fig. 9. 
Proceed in this manner until 7 twisted taps 
have been taken off at every 10 turns. After 
these first 70 turns have been wound on the 
tube then take off a 6 inch twisted tap for 
every succeeding single turn until 10 addi- 
tional turns have been wound on the tube. 
After winding the last turn of wire anchor 
the end by weaving it through two holes 
punched in the tube much as was done at the 
start, leaving about 12 inches of wire free for 
connecting. It is to be understood that each 
of the 18 taps is slightly staggered from the 
one just above, so that the several taps w T ill 
not be bunched along one line on the card- 
board tube. See Fig. 9. It would be ad- 
visable, after winding the tuner as just de- 
scribed, to dip the tuner in hot paraffin. This 
will help to exclude moisture. 

Upright Panel and Base — Having com- 
pleted the tuner to this point, set it aside and 
construct the upright panel shown in Fig. 10. 



4 o AMATEUR RADIO 

This panel may be a piece of wood approxi- 
mately Yz inch thick. The position of the 
several holes for the binding posts, switch 
arms and switch contacts may first be laid out 
and drilled. 

The "antenna" and "ground" binding posts 
may be ordinary }i inch brass bolts of suffi- 
cient length and supplied with three nuts and 
two washers. The first nut binds the bolt to 
the panel, the second nut holds one of the 
short pieces of stiff wire, while the third nut 
holds the antenna or ground wire as the case 
may be. The switch arm with knob shown 
at V, Fig. 9, may be purchased in the as- 
sembled form or it may be constructed from 
a thin slice cut from a broom handle and a 
bolt of sufficient length equipped with four 
nuts and two washers together with a narrow 
strip of thin brass somewhat as shown. 

The switch contacts (W, Fig. 9) may be 
of the regular type furnished for this purpose 
or they may be brass bolts equipped with one 
nut and one washer each or they may even be 
nails driven through the panel with an in- 
dividual tap fastened under the head or 
soldered to the projection of the nail through 
the panel. The switch contacts should be just 
close enough that the switch arm will not drop 



AMATEUR RADIO 41 

between the contacts, but also far enough apart 
that the switch arm can be set so as to touch 
only one contact at a time. 

The telephone binding post should prefer- 
ably be of the set screw type as shown at X, 
Fig. 9. 



CHAPTER VII 



THE WIRING OF A CRYSTAL SET 

Directions for Operating — Uses of Test Buzzer — Approxi- 
mate Cost of Parts of Home-made Crystal Set 



Having constructed the several parts men- 
tioned in previous chapter and mounted them 
on the wood base, one is ready to connect the 
several taps to the switch contacts and attach 
the other necessary wires. Scrape the cotton 
insulation from the loop ends of the sixteen 
twisted taps as well as from the ends of the 
two single taps coming from the first and last 
turns. Fasten the bare ends of these wires to 
the proper switch contacts as shown by the 
corresponding numbers in Fig. 9. 

One should be careful not to cut or break 
any of the looped taps. It would be prefer- 
able to fasten the connecting wires to the 
switch contacts by binding them between the 
washer and the nut as shown at 3, Fig. 9. 
A wire is run from the back of the binding 
post marked "ground" (Fig. 9) to the back 
of the left-hand switch-arm bolt (Y), thence 

42 



AMATEUR RADIO 43 

to underneath the left-hand binding post 
marked "phones." 

A wire is then run from underneath the 
right-hand binding post marked "phones" to 
underneath the binding post (4, Fig. 9), 
which forms a part of the crystal detector. 
A piece of No. 24 bare copper wire about 
2^ inches long, one end of which is twisted 
tightly around the nail (the nail passing 
through binding post 4), the other end of 
which rests gently by its own weight on the 
crystal (1). 

The bare copper wire which was wrapped 
tightly around the three brass wood-screws 
holding the crystal in place is lead to and fas- 
tened at the rear of the right-hand switch arm 
bolt (v), thence to the upper left-hand bind- 
ing post marked "antenna." As much as pos- 
sible of this wiring is shown in Fig. 9. 

After all the parts of this crystal-detector 
radio receiving set*have been constructed and 
assembled the first essential operation is to ad- 
just the little piece of wire, which rests lightly 
on the crystal, to a sensitive point. This may 
be accomplished in several different ways; the 
use of a miniature buzzer transmitter is very 
satisfactory. Assuming that the most sensi- 
tive point on the crystal has been found by 



44 AMATEUR RADIO 

method described in paragraph below, "The 
Test Buzzer," the rest of the operation is to 
get the radio receiving set in resonance or in 
tune with the station from which one wishes 
to hear messages. 

The tuning of the receiving set is attained 
by adjusting the inductance of the tuner. 
That is, one or both of the switch arms are 
rotated until the proper number of turns of 
wire of the tuner are made a part of the me- 
tallic circuit between the antenna and ground, 
so that together with the capacity of the an- 
tenna the receiving circuit is in resonance with 
the particular transmitting station. It will 
be remembered that there are 10 turns of wire 
between each of the first 8 switch contacts and 
only one turn of wire between each 2 of the 
other contacts. 

The tuning of the receiving set is best ac- 
complished by setting the right-hand switch 
arm on contact (1) and rotating the left-hand 
switch arm over all its contacts. If the de- 
sired signals are not heard, move the right- 
hand switch arm to contact (2) and again ro- 
tate the left-hand switch arm throughout its 
range. Proceed in this manner until the de- 
sired signals are heard. 

It will be advantageous for the one using 



AMATEUR RADIO 45 

this radio receiving equipment to find out the 
wave frequencies (wave-length) used by the 
several radio transmitting stations in his im- 
mediate vicinity. 

The Test Buzzer (Z, Fig. Q) — As men- 
tioned previously, it is easy to find the more 
sensitive spots on the crystal by using a test 
buzzer. The test buzzer is used as a minia- 
ture local transmitting set. When connected 
to the receiving set as shown at Z, Fig. 9, the 
current produced by the buzzer will be con- 
verted into sound by the telephone receivers 
and the crystal, the loudness of the sound de- 
pending on what part of the crystal is in con- 
tact with the fine wire. 

To find the most sensitive spot connect the 
test buzzer to the receiving set as directed, 
close the switch (5, Fig. 9) (and if necessary 
adjust the buzzer armature so that a clear note 
is emitted by the buzzer), set the right-hand 
switch arm on contact point No. 8, fasten the 
telephone receivers to the binding posts 
marked "phones," loosen the set screw of the 
binding post slightly and change the position 
of the fine wire (6, Fig. 9) to several posi- 
tions of contact with the crystal unit until the 
loudest sound is heard in the phones, then 
tighten the binding post set screw (4) slightly. 



46 AMATEUR RADIO 

Approximate Cost of Parts 

The following list shows the approximate 
cost of the parts used in the construction of 
this radio receiving station. The total cost 
will depend largely on the kind of apparatus 
purchased and on the number of parts con- 
structed at home. 

Antenna — 

Wire — Copper, bare or insulated, No. 
14, 100 to 150 ft, about $ .75 

Rope — y% or y 2 inch. 2c per foot. 

2 insulators, porcelain 20 

1 pulley 15 

Lightning switch — 30 ampere battery 

switch 30 

1 porcelain tube 10 

Ground connections — 

Wire (same kind as antenna wire.y 

1 clamp 15 

1 iron pipe or rod 25 

Receiving set — 

y 2 pound No. 24 copper wire double 

cotton covered 75 

1 cardboard box. 

2 switch knobs and blades complete. . 1.00 
18 switch contacts and nuts 75 

3 binding posts — set screw type 45 

2 binding posts — any type 30 

1 crystal — tested 25 

3 wood screws, brass, y in. long 03 



AMATEUR RADIO 47 

Wood for panels (from packing box.) 

2 pounds paraffin 30 

Lamp cord, 2 to 3c per ft. 

Test buzzer 50 

Dry battery 30 

Telephone receivers 4.00 to $8.00 

Total $11.00 $15.00 

If nothing but the antenna wire, lightning 
switch, porcelain tube, crystal, telephone re- 
ceiver, bolts and buzzer are purchased this 
total can be reduced to about $6.oo. 



CHAPTER VIII 



VACUUM TUBES 

The V. T. the Keystone of Modern Radio — Invented by an 

Englishman, Perfected by an American — Difference 

Between Two and Three-Element Tubes 



WHAT is the vacuum tube that has so revo- 
lutionized radio telephony? What is this 
thing that looks like an electric light bulb, yet 
makes audible the electro-magnetic waves 
that reach it from the air, via the aerial? 

The vacuum tube made the radiophone 
famous. The V. T., as it is called for short, 
is the very keystone of the arch of modern 
wireless telegraphy. Without it this kind of 
telegraphy, or telephony, would have a very 
restricted use. With it we can telephone 
from Washington to Honolulu and from New 
York to Paris or London — and telegraph be- 
tween these points at a rate of a hundred 
words or more a minute. 

We can speak telephonically to flying air- 
planes or airships one hundred miles away, 

and miles high in the sky. We can talk from 

48 






AMATEUR RADIO 49 

ship to ship across stormy seas many hundreds 
of miles as easily and often better than we can 
speak across the city by means of the ordinary 
land telephone. 

In short the V. T. is an invention worthy to 
stand in the same category of merit as the 
steam engine, the power loom, the sewing ma- 
chine or the gasoline engine. Moreover, un- 
like these inventions, it is extremely simple in 
construction. 

Invented by Professor Fleming, an English- 
man in 1904, an addition was made to it in 
1907 by an American, Lee DeForest. This 
addition consists in the interposition of a zig- 
zag of wire between the filament and the 
metal plate of the Fleming oscillation valve. 

This addition formed the starting point for 
new developments by numerous inventors in 
America, England and France, which have 
finally given us the remarkable appliance 
called the three electrode vacuum tube. The 
modern V. T. can not only detect but can also 
magnify feeble electric oscillations, and, more 
important still, can generate very powerful 
vibratory electric currents if the circuit con- 
necting the outer cylinder to the filament con- 
tains a battery or dynamo creating a steady 
electric voltage, and if this circuit is properly 



5 o AMATEUR RADIO 

connected to another circuit joining the per- 
forated plate or grid with the filament. 

In this form it is called a transmitting valve, 
and we can by it generate the very powerful 
high frequency, or alternating electric, cur- 
rents in an aerial wire which are necessary in 
wireless telegraphy or telephony. 

These electric vibrations generate the elec- 
tric waves which travel away through space 
from the aerial. 

The aerial wire, therefore, resembles a sort 
of lighthouse which is radiating invisible 
light. 

Transmitting valves are now made with 
silica or glass bulbs about the size and shape 
of a football. A large number can be har- 
nessed together so as to generate enormous 
oscillatory currents. 

At their great Carnarvon wireless station 
on the side of Mount Snowdon, Wales, Mar- 
coni's Wireless Telegraph Company have 
built a valve panel containing about sixty 
large valves, which can put into the great 
aerial wires currents of three or four hundred 
amperes. The electric waves so generated 
can be detected by suitable receiving appa- 
ratus, using audions as detectors and ampli- 
fiers, at all parts of the habitable earth. 



AMATEUR RADIO 51 

There are two other methods of creating 
the continuous electric waves now used in 
wireless telegraphy. One of these is by means 
of a high-frequency alternator, which is a 
complicated kind of dynamo not very differ- 
ent in principle from the alternators used for 
producing the low-frequency electric currents 
employed in electric lighting. 

Machines of this kind are installed in the 
great wireless stations at Long Island and at 
St. Assise, near Paris. Again, there is an- 
other method w r hich makes use of an electric 
arc. The audion tube has, however, great ad- 
vantages in point of first class cost as against 
the high-frequency alternator, and it is su- 
perior to the arc generator because it gives a 
purer form of electric wave, less contaminated 
by a mixture of waves of various wave-lengths, 
called harmonics, and has other advantages 
in economy of power in signalling. 

The growth and development of the three 
methods of electric wave generation — namely, 
by high-frequency alternators, arc, and trans- 
mitting tubes — will be watched by experts 
with great interest. 

The Fleming valve was a small incandes- 
cent lamp highly exhausted of air and contain- 
ing a filament of either tungsten or platinum 



5 2 AMATEUR RADIO 

wire which could be rendered intensely hot 
by passing an electric current through it. 
Fleming discovered that if a cold plate were 
also inserted in the tube it had a rectifying 
effect when used in wireless telegraphy. It 
was an improvement on the crystal. 

Then DeForest as already stated developed 
the tube by putting another element in it 
which he called the "grid." The outer cylin- 
der of this is formed of a solid plate of nickel; 
the inner one is either a spiral of nickel wire 
or else a cylinder of nickel gauze or network. 
These two cylinders do not touch each other 
or the filament, and they are attached to wires 
which are sealed through the wall of the bulb. 
(See Fig. n.) 

To explain the operation of this device I 
must remind the reader that modern research 
has shown that the atoms of which material 
substance are composed are themselves formed 
of still smaller atoms of electricity called elec- 
trons. 

An atom of matter is a very small thing. 
If 250,000,000 atoms of copper or gold were 
put in a row, like marbles, touching each 
other the row would only be an inch long. 
But an electron is still smaller. Its diameter 
is probably only one hundred-thousandth of 



dRtD 



FU.AME1NT 



ELECTRONS 



BASL 




LULU UJ UJ 



PLATE. 



TERMINALS 

Diagram of Audion Tube, Showing 
Relative Positions of Elements 



WIRE 



MAGNETIC 
FIELD-*- 




Fig 11 



—J T~ 

To Battery To Battery 



54 AMATEUR RADIO 

that of an atom. Electrons are of two kinds, 
positive and negative, and an atom is a sort of 
solar system in which a number of negative 
electrons revolve round a nucleus composed 
chiefly of positive electrons. In the case of 
metals some of these negative electrons escape 
easily from the atoms and probably jump 
about from atom to atom like bees in a garden 
flitting from flower to flower. 

The state we call an electric current in a 
wire is merely these free electrons as a whole 
drifting in one direction, or surging to and 
fro without ceasing their irregular motion. 
When a wire, say, of tungsten, is made very 
hot some of these free electrons escape from 
its surface, and this is called thermionic emis- 
sion. If, then, we surround the hot wire by 
a cylinder of cold metal which is electrified' 
positively, the escaping electrons are attracted 
to it, and the movement of negative electrons 
from the hot wire to the cold plate creates a 
thermionic current. 

Since, then, negative electricity can pass 
from the hot wire to the cold metal cylinder, 
but cannot pass in the opposite direction, such 
a lamp, with cylinder enclosing the filaments, 
acts toward electricity as a valve in a pump 



AMATEUR RADIO 55 

acts toward water. It allows a flow to take 
place in one direction only. Prof. Fleming 
who was the first to use, in 1904, such an ap- 
pliance in wireless telegraph, called it, as I 
have already said, an oscillation valve, a name 
subsequently changed to thermionic valve, 
and finally to vacuum tube. 

The more anxious one becomes to obtain 
the best possible results from a receiving set 
the more necessary it is to pay proper attention 
to the plate voltage applied to the tubes. In 
detector tubes the most desirable voltage as 
shown by the characteristic curves is approxi- 
mately 2 1 -volts, and any large variation from 
the value will affect the quality and loudness 
of the reception. 

In amplifying tubes the loudness of recep- 
tion is materially increased by increasing the 
plate voltage which, with the ordinary tube, 
should be between 40 and 100-volts. Unless 
a voltmeter is used there is no quick way of 
knowing whether the B-battery is in good 
order. Should there be any failure of the 
battery or the circuit, the voltmeter indicates 
the trouble immediately. 

It is sufficient to use one voltmeter and pro- 
vide a selector switch or jack for connecting 



56 AMATEUR RADIO 

the voltmeter either to the detector or ampli- 
fier plate circuits, and, for this reason, it is 
desirable to select either a 50-volt or a 100-volt 
range instrument, depending upon the highest 
voltage used on the amplifier tubes. 



CHAPTER IX 



PRINCIPLES OF V.T. TRANSMISSION 

How Music and the Human Voice are Sent Through the 

Ether by the "Little Bottles"— Different Methods 

of V. T. Transmission 



NOW let me briefly discuss the general prin- 
ciples of the vacuum tube as used in wireless 
telephony transmission. It is usual in wire- 
less telephony to send out a steady stream of 
waves and to vary this stream by means of the 
sound vibrations of the voice. 

This steady stream of waves can be obtained 
by means of various kinds of CW generators. 
The continuous stream, if received by an ordi- 
nary non-oscillating detector, will produce no 
sound whatever. If, however, the steady 
stream be modulated or varied by means of a 
microphone so connected in the transmitter 
circuit as to vary the amplitude of the con- 
tinuous waves when the microphone is spoken 
into, the rectified signals at the receiving sta- 
tion will consist of a varying direct current. 

57 



5 8 AMATEUR RADIO 

These variations will actuate a telephone 
receiver and produce, sound waves of exactly 
the same nature as those produced by the 
speaker at the transmitting station. 

The action is somewhat analogous to that 
of a simple telephone circuit consisting of a 
microphone, a battery, and a telephone re- 
ceiver in series. A steady current flows from 
the battery through the microphone and 
through the telephone receiver. 

This steady current produces normally no 
effect on the telephone receiver. If, however, 
the microphone be spoken into, its resistance 
will be varied and the steady current in the 
circuit will vary in strength, producing a 
sound in the receiver corresponding to the 
original speech. 

In radio telephony a steady stream of waves 
is usually modulated by means of a micro- 
phone, the audio-frequency variations gen- 
erally occurring at rates from iog to 2,000 per 
second, the average frequency (sometimes 
termed the "mean speech frequency") being 
about 800 to 1,000 per second. 

Two general methods of modulation are 
used at present; either the amplitude of the 
continuous waves is varied by the microphone, 
or the wave length is altered. 



AMATEUR RADIO 59 

If the receiving station is tuned to the 
carrier wave arry variations of the wave-length 
of the latter will produce mistuning, and con- 
sequently a decrease of response in the re- 
ceiver, depending on the degree of the varia- 
tion. Sometimes both wave-length and am- 
plitude modulation occur at the same time. 

Some of the methods of modulating the 
continuous stream waves are : 

(1) Connecting a microphone directly in the 
earth lead of a CW transmitter. 

(2) Coupling a microphone circuit to one of 
the oscillatory circuits of a CW trans- 
mitter. 

{3) Varying the output of a CW transmitting 
vacuum tube by using a microphone to 
vary the grid potential. 

(4) The use of an additional grid, whose po- 
tential is varied by means of a micro- 
phone. 

(5) Variation of the anode voltage or anode 
current of an oscillating transmitting 
tube by means of a microphone. 

(6) Varying the output of an amplifying 
valve coupled to the aerial. The grid 
circuit is separately excited by a source 
of high frequency current and a micro- 



60 AMATEUR RADIO 

phone arrangement affects the output of 
the amplifier valve in one way or another. 

(7) Causing a microphone to vary the resis- 
tance of an energy absorbing conductor 
connected across the aerial circuit coupled 
to the aerial circuit. 

(8) The microphone is made to limit the 
oscillations in the grid circuit of an 
oscillator* 

(9) The microphone varies the retroaction 
of an oscillating valve. 



CHAPTER X 



OPERATION OF TUBES 

Dangers to be Avoided — Why Filaments of Transmitting 

Tubes Should Be Energized by Alternating Current — 

How to Test Tube Circuits — Buzzer Modulation 



ALTHOUGH the principles of construction 
and operation in the larger power tubes are 
no different from those applying in the case of 
the smaller ones, many effects that are negli- 
gible in the latter are somewhat magnified in 
the case of the larger tubes, and certain pre- 
cautions are therefore necessary. The ma- 
jority of accidents to power tubes and to their 
auxiliary apparatus occur during the period 
of development of circuits and testing and ad- 
justment, rather than during operation, and a 
little care in making these adjustments will 
prove of advantage. 

The following points, briefly enumerated, 
are all of importance and should be studied 
before the set is put into operation. Limited 
space prevents going into detail as to the 
reasons for some of the instructions herein laid 

61 



62 AMATEUR RADIO 

down, but the amateur may be assured that 
they are the results of practical observation 
and experiment, and that he cannot well 
afford to ignore them. 

The life of power tubes may be prolonged 
by mounting them in the proper position. 
Some should be operated in a vertical posi- 
tion, whereas others may be operated in either 
a vertical or a horizontal position. Instruc- 
tions are given with the different makes of 
tubes. If mounted horizontally the plate 
should lie in a vertical plane with the seal-off 
tipped down. In powerful C.W. transmit- 
ting sets the circuit should be so arranged that 
the center tap on the filament coil, and also 
the negative lead of the direct current high 
voltage source, are both at ground potential 
relative to high frequency potentials in order 
to insure safety. 

Great care should be taken to thoroughly 
insulate the grid and plate leads to the tubes, 
and the coil sections connected to these leads 
or any apparatus in them. 

In order to guard against excessive transient 
voltages in connection with V.T. tubes a pro- 
tective gap should be provided at, or near, the 
socket terminals between the grid and term- 
inal and one of the filament terminals. One- 



AMATEUR RADIO 63 

sixteenth of an inch is correct for a 50-Watt 
tube, and one-eighth of an inch for a 250-Watt 
tube. 

Occasionally, in the parallel operation of 
power tubes, ultra high frequency oscillations 
develop in the plate and grid circuits, which 
prevent the realization of full output and 
cause excessive plate and grid currents. This 
effect may be avoided by inserting an induc- 
tance of a few micro-henries (ten turns in one 
layer on a tube one inch in diameter is sug- 
gested) in one or more of the individual grid 
leads of each tube as close to the grid terminal 
of a socket as possible. The protective gap 
should be placed between this coil and the 
grid terminal of the socket. The best ar- 
rangement is to mount a gap directly on the 
socket terminals and one terminal of the coil 
directly to the grid terminals of the socket. 

One method of modulation employed in a 
vacuum tube radio transmitting equipment 
utilizes a tube as a modulator in addition to 
the oscillator tube. The plate current for 
these two tubes is fed through an audio fre- 
quency reactance. In a radio telephone trans- 
mitting equipment the degree of modulation 
is of equal importance to the amount of an- 
tenna current as far as the strength of the re- 



64 AMATEUR RADIO 

ceived speech is concerned. The antenna 
ammeter does not usually indicate whether 
the output is being modulated in a normal 
manner. One method of checking this is to 
insert a small lamp in the plate circuit of the 
amplifier. This flashes up when the micro- 
phone is spoken into and acts as an operating 
indicator of the microphone and modulation 
circuits. A type of lamp should be chosen 
that will show a low degree of brilliancy with 
the plate currents obtained on the tubes used. 
Even for the five-Watt size of tubes these 
lamps are easily obtainable. Try miniature 
lamps of the automobile type. 

The filaments of transmitting power tubes 
are preferably energized by alternating cur- 
rent which gives an added factor of safety and 
prolongs the filament life. 

In adjusting the temperature of a filament 
the amateur should always use a voltmeter 
rather than an ammeter, and the voltmeter 
should be connected directly to the socket con- 
nections in order that the voltage drop across 
the filament may be measured. If tungsten 
filaments are operated at constant voltage 
rather than constant current, it will increase 
their life in the ratio of three to one. 

If alternating current is not available the 



AMATEUR RADIO 65 

filaments may, of course, be energized from a 
D.C. source of suitable E.M.F. It is empha- 
sized, however, that the life of a vacuum tube 
is considerably prolonged by A.C. filament 
excitation, and particularly if the filament 
voltage is maintained at constant value. 

A "blow-out" of the vacuum tube is the 
bogey that haunts many an amateur who has 
been out-of-luck with his V.T.'s. 

It is unwise to overload a radiotron or any 
other power tube continuously, as its operat- 
ing life will be seriously curtailed. It is a 
much better plan and more economical to 
operate two tubes in parallel than it is to 
force one tube to deliver a power output far 
in excess of w T hat it is rated for; in fact great 
economy will result from burning tubes 
slightly below normal brightness. 

For instance, it can be shown that to double 
the filament emission will reduce the operat- 
ing life of the tube to one-fourth, whereas, by 
operating the filament at 95% of its rated volt- 
age, the life will be doubled. 

When first testing the circuit, or when the 
set has not been operated for some time, it is 
wise to cut down all voltages to one-third of 
the normal voltage. This will greatly reduce 
the possibility of burning out the tube through 



66 AMATEUR RADIO 

a wrong connection which has been over- 
looked, as a fault will then instantly be de- 
tected before the damage is done. 

In a radio telephone transmitting circuit of 
the usual type a modulator tube is employed 
and a buzzer is often substituted for the 
microphone when it is desired to send out 
interrupted continuous waves. This imposes 
voltage strains on the oscillator tube, and if an 
over-voltage is also applied to its plate the 
voltage between grid and filament may be ex- 
cessive. The protective gaps described in a 
previous paragraph are a safeguard against 
breakdown due to this voltage. 



CHAPTER XI 



AERIALS 



The Functions of Antennae — Hints on Construction of 

Aerials — Different Types of Aerial — "Skin Effect" 

on Different Kinds of Wire 



ALTHOUGH any alternating current will 
cause a disturbance in the ether regardless of 
the size or shape of the circuit, in order to 
create the maximum disturbances possible 
with the power available, it is necessary to 
erect an "aerial." 

An aerial or antennae is a system of wires 
stretched above the surrounding objects and 
connected to the radio set. The aerial can be 
used for either transmitting or receiving, a 
switch or other transfer means being used to 
connect it to one or the other according as the 
station is sending or receiving messages. 

The wire used in aerials is either bare cop- 
per, phosphor-bronze, or copper clad steel 
and sometimes galvanized iron. The ends of 
the wires are insulated with specal insulators 

and the wire lead into the house through an 

67 



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•8 

< 



CO 



8 

<3 




AMATEUR RADIO 69 

insulating tube known as a "bulkhead" insu- 
lator. 

In the installation of a receiving set for the 
reception of wireless telegraph or telephony, 
the following hints with regard to the antenna 
may be of some value. 

Care should be exercised in the selection of 
a site for the erection of the antenna. Avoid 
placing an antenna in such a position that its 
wires are parallel to lighting lines, high ten- 
sion power lines or telephone lines. If there 
are any such wires near the contemplated site, 
be sure to erect your aerial so that its plane 
will be at right angles to and as far as possible 
away from such wires. It is very important 
to observe these precautions if the best results 
are to be obtained. 

The antenna may be erected between two 
trees if available or from the corner of a house 
or building. The best method, however, is to 
erect two masts and support the antenna be- 
tween these. 

The antenna may be erected at any con- 
venient height. The higher the antenna, how- 
ever, the better will be the results. An an- 
tenna erected at a good height away from sur- 
rounding buildings is less liable to pick up 
static, which greatly interferes with the recep- 




Modern Amateur Antenna Installation. 



WTrefaxz 




Overhead View of Same. 



AMATEUR RADIO 71 

tion of radio signals, especially music or 
speech. 

There are numerous types of aerials which 
may be used for receiving purposes. The 
best types for the amateur will be either 
the straight-away inverted "L" type or the 
straight-away "T" type. These aerials re- 
ceive their name from the method of connec- 
tion of the lead in wire. In the inverted 
"L" type the lead-in is connected from the 
end of the aerial while in the "T" type the 
lead-in wire is taken from the center of aerial. 
The inverted "L" type is generally employed 
and is the better for receiving. 

The aerial may consist of any number of 
wires. While a one-wire^ aerial will give ex- 
cellent results in receiving, an aerial consisting 
of two or four wires has greater capacity and 
is to be preferred. If it is desired to receive 
from short wave-length stations, we would 
suggest that aerial be not more than 100 feet 
in length. 

Another important feature in connection 
with the antenna is the lightning ground con- 
nection. All antennae should be "grounded" 
when not in use. An antenna properly 
grounded acts as protection against lightning 
in the same manner as lightning rods neutra- 





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FROM CHWirO to 

CHIMNEY 
75 TO 100 FEET 
SINGLE ANTENNA 



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75 TO »00 FEET 



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AMATEUR RADIO 73 

lize static charges in its vicinity. A good 
ground connection may be made to a water 
pipe or if such is not available to a rod or 
pipe driven into the earth in a damp spot. A 
single pole, double throw-switch of large ca- 
pacity should be placed in circuit between the 
aerial lead and the ground connection, No. 4 
stranded rubber covered wire being used for 
connection from the ground switch to the 
ground connection. 

A ground connection must also be provided 
for the instrument. This may be made on a 
water pipe, a radiator or any metal which is a 
good conductor of electricity and which is also 
connected to the earth. No. 12 or 14 wire 
may be used for connection from the ground 
to the instruments. 

Radio frequency currents, conducted by 
wires at the sending and receiving stations, 
travel only along the surface exterior of the 
wires and do not penetrate to the core, because 
of the phenomenon known as "skin effect." 
The loss of radio energy in the wires depends 
on the electrical conducting properties of the 
surface metal. 

In so far as electrical conducting properties 
are concerned, pure copper is the most 
efficient commercial metal, but it lacks suffi- 



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FROM WATER TANK TO FLAG \ . 
•POLE. OR OTHER PROJECTION J 



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TO HOLD WIRE AT LEA3T X FEET 
FROM ANY WALU.. 



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2 FRon chimney to roof door 

75 -TO 100 FEET/SINGLE ANTENNA 



76 AMATEUR RADIO 

cient strength for a great many purposes. 
Bronze is also objectionable because of its 
poor electrical conductivity- — approximately 
two-fifths as much as copper of equal size. 
Much more radio energy is lost in bronze wire 
than in copper. 

The core of a wire carries no radio fre- 
quency current and performs no electrical 
service, because of this radio frequency phe- 
nomena called "skin effect." The core may 
therefore be made to perform a greater me- 
chanical duty. Hence the ideal wire for 
radio antenna should have a core of great 
strength (steel) and an outer covering of high 
conductivity (copper). 



CHAPTER XII 



GROUND CONNECTIONS 

Common Faults of Aerials — How to Put a Metal Roof to 

Use — Proper Place for the Lead-in — Uses 

of the Counterpoise 



If you have not a good aerial and your 
ground connections are defective you cannot 
expect to be able to sit in on the radio broad- 
casting concerts. 

The commonest faults with aerials are that 
they are too short and are not far enough from 
the ground. You cannot expect to be able to 
pick up much with ten or fifteen feet of wire 
strung near to the earth like a clothes-line. 

The aerial should be at least fifty feet clear 
of all obstructions if you are using a crystal 
set. Of course, if you have an audion detec- 
tor, then height is not so essential. However, 
even with a vacuum tube the aerial should 
not be less than twenty-five feet above the 
ground or roof. 

For receiving sets it is not necessary to use 

costly copper or bronze wire for your aeria). 

78 



AMATEUR RADIO 79 

Galvanized iron wire, which may be bought 
for about four feet for a cent, is good enough. 
A single wire aerial is just as good for receiv- 
ing as a two or more wire antenna. The in- 
sulators may be simply porcelain cleats that 
may be purchased at any electrical store for 
two cents apiece. Be sure and have the 
lead-in clear of tin roofs and gutters. 

By the way, if you have a metal roof on 
your house this need not be a hindrance to re- 
ception. If your aerial is over the tin roof 
solder a lead to the roof and connect it to- 
gether with the usual ground wire to the post 
marked "ground" on the receiving set. This 
is especially helpful in receiving music. 

When making the ground connection to the 
water pipe or radiator do not merely wrap the 
wire around. Solder it. The lead-in from 
the aerial should also be soldered where it 
makes the connection with the aerial. 

For efficiency the lead-in should be con- 
nected to the aerial at the end nearest to the 
broadcasting station. That is, if the trans- 
mitting station is to the west of your receiving 
station, the aerial should be hung from east to 
west with the lead at the western end. If 
there is broadcasting both sides of you put the 
lead-in in the middle of your aerial. 



80 AMATEUR RADIO 

Because of their compactness, and because 
they do away with the necessity of crawling 
up on roofs to adjust antennae, loop aerials 
are becoming increasingly popular with 
owners of radiophone receivers. 

It is the loop aerial that is used in direction 
finding work. Radio compass stations are 
erected all along the coast of the United 
States and other countries, enabling ships to 
determine their exact position at any time in a 
fog or heavy storm in which they might be 
carried out of their courses. 

The same system is used on airplanes to en- 
able the pilots to know their direction when 
flying in the clouds, or at night, and at the 
present time this device is being used with suc- 
cess on a number of our Army and Navy ma- 
chines. 

Undoubtedly owing to its many advan- 
tages over the ordinary type of antenna the 
loop aerial is the aerial of the future, but 
further improvements must be made in order 
to perfect this wave collector. 

A loop aerial suitable for receiving the 
broadcasted music should be about four feet 
square, wound with thirty-five turns of No. 
8 D.C.C. wire mounted so that it can be ro- 



AMATEUR RADIO 81 

tatcd. Remember that a loop aerial cannot 
be used with a crystal receiving set unless you 
are within two or three miles of the trans- 
mitting station, and even then you would get 
very poor results with it. 

With an audion receiver a loop is effective 
anywhere within thirty miles of the trans- 
mitter, and with an audion detector and 2-step 
amplifier the loop will be effective up to 500 
or 800 miles for telegraph signals, but for 
telephone work for not more than 200 miles. 

Some loop enthusiasts use a ground con- 
nection also with a loop connected to the usual 
ground post on the receiver. This brings in 
the signals much clearer, although if the loop 
is used for direction-finding work, a ground 
connection cannot be used. 

A loop aerial helps greatly to eliminate 
static, and during the summer months when 
the static is usually troublesome, the radio- 
phone fan should experiment with different 
sizes of loops and different hook-ups. 

A good idea when attempting to receive 
long distance signals, or "DX work," is to 
construct a counterpoise. 

A counterpoise is an antenna constructed 
near the ground. It is the same as the more 



82 AMATEUR RADIO 

familiar antenna except that it is used in place 
of a ground connection. It must be at least 
one foot above the ground. 

In localities that have sandy or very rocky 
soil this will help materially in bringing in 
distant stations. You may not notice any 
great difference at first, but on the first clear 
cold night the distant stations will roll in. 
Try it with the ground lead and then without 
it. 

With a C.W. (continuous wave) transmit- 
ting set I have, when using a regular water- 
pipe system, radiated only two-tenths of an 
ampere. After building a counterpoise the 
radiation jumped to eight-tenths of an am- 
pere. Don't miss any chance you may get to 
add another ground connection. 

Before the war I had a crystal receiving set 
which consisted of a double slide tuning coil, 
a fixed condenser and a pair of phones along 
with a galena detector. There was no music 
to listen to in those days, and one had to learn 
the code before he could get any "dope" out 
of the air. 

I had a ground connection to a well about 
ioo feet deep, and at first this seemed to serve 
very well. One day I constructed an aerial 
for receiving Arlington as the tuning coil 



AMATEUR RADIO 83 

would not go above 1800 meters. It snowed 
the first night, and the storm carried away the 
makeshift antenna. Of course this grounded 
my regular antenna, and I had to disconnect 
the new antenna from the set. 

Noticing that the far end of it was lying in 
the snow I connected it to the ground wire on 
the antenna switch. A great difference in sig- 
nal strength was at once noticed. WSE and 
NAH came in clearly and loudly. My sta- 
tion w r as about forty miles from New York. 
The first night I heard WBF, NAM and 
NGE, and 'a few others which I had never 
picked up before. 



CHAPTER XIII 



STATIC 



Nature's Own Transmitter — The Action of Lightning on 

Receiving Sets 

Lightning, "summer static," nature's own 
wireless transmitter, is the bugbear of amateur 
radio. 

Static is more troublesome to the more sen- 
sitive receiving sets where several steps of 
amplification are in use. Static is more pre- 
valent in summer, due to the higher tempera- 
ture of the air. Heat electricity is formed in 
the air and gradually collects upon the an- 
tenna until a sufficient charge has been built 
up to break down the natural resistance of the 
receiving set. 

It then discharges through the primary of 
the receiving transformer to the ground. Due 
to the highly dampened quality of this dis- 
charge it permeates the whole receiving set 
and can not be tuned out. 

Another cause of static is the close prox- 

84 



AMATEUR RADIO 85 

imity of two clouds, one of which is charged 
with negative electricity, the other with posi- 
tive. The resulting spark discharge sets up 
a chain of highly dampened oscillations which 
are impossible to tune out. 

These "strays" as they are called, are much 
more prevalent on long waves than on the 
shorter ones used by the broadcasting stations. 
In summer, when static is so strong on, say, 
10,000 meters that nothing but a continuous 
roar can be heard, only occasional static 
scratches will be heard on 200 meters. 

No practical method has yet been dis- 
covered that will eliminate static, although 
there are ways by which it may be reduced. 
The most common method is by the use of a 
very loose coupling between primary and sec- 
ondary of the receiving transformer. By tun- 
ing the secondary into very close resonance 
with the primary at such frequency at which 
reception is desired, the signal will readily 
pass through — but moderate strength static of 
no definite wave length will pass through to 
ground without affecting the secondary cir- 
cuits in respect to which it is out of resonance. 
The very strong static will, however, force it- 
self into the secondary. 

Another method for reducing static is by the 



86 AMATEUR RADIO 

use of an antenna of small capacity; that is, 
one that offers only a small surface for 
"strays" to collect on. An antenna having 
one wire will have this effect. A loop an- 
tenna, due to its high directional qualities, 
will almost entirely eliminate horizontal static 
(that which comes from a long distance, 
caused by a distant storm). This will not 
overcome local static, however. 



CHAPTER XIV 

THE ARMSTRONG FEED-BACK CIRCUIT 

Regenerative Circuit Most Revolutionary Contribution to 
Wireless Art — The Discovery One of the Ro- 
mances of Radio — How it Made Mod- 
ern Broadcasting Possible 

THE most important contribution to radio 
art since the perfection of the vacuum tube is 
the much-discussed "Armstrong Feed-Back 
Circuit." But for Armstrong's circuit there 
would be no such thing as radiophone trans- 
mitting by means of vacuum tubes. In other 
words, but for Armstrong you could not get 
the wonderful musical programs and other 
forms of entertainment that are now daily 
broadcasted by hundreds of stations through- 
out the United States. 

Certainly an arc transmitter could be used, 

but the sounds that would be projected 

through the air by this means would be so 

inextricably mixed up with "clicks, hisses, 

gurgles and howls" that nobody would have 

the patience to listen to it. No trans-Atlantic 

87 



AMATEUR RADIO 89 

conversation can be carried on without the 
Armstrong principle being employed; even 
the modern multiplex form of wireless teleg- 
raphy and telephony must pay tribute to Arm- 
strong. 

Edwin H. Armstrong is a young American. 
The story of his discovery is one of the great 
stories of radio. He became interested in 
wireless when a boy in short pants. When he 
first hit upon his "idea" he could not for a 
long time get anybody interested in his work. 
How could he discover anything? He was 
too young! Finally Professor Michael I. 
Pupin, Director of the Marcellus Hartley Re- 
search Laboratory of Columbia University, 
with whom he was at the time studying, 
placed at his disposal the facilities of the 
Hartley laboratory in which to perfect his in- 
vention. This is Prof. Pupin's tribute to 
Armstrong: 

"The Armstrong Feed-Back Circuit is one 
of the most important, if not the most impor- 
tant, invention in the wireless art. It is the 
invention of employing in connection with an 
audion a coupling which enables a local bat- 
tery to contribute its energy to the amplifica- 
tion of a signal received in a wireless station. 
The contribution obtained in this manner 



go AMATEUR RADIO 

from the local battery or the local source of 
energy may be made as large as we please 
within certain definite limits. Armstrong 
was the first to employ this coupling — or as 
it is called, the 'Armstrong Feed-Back Cir- 
cuit,' and he did it while he was still an under- 
graduate at Columbia University. 

"The invention enabled him to make an- 
other most important step in wireless teleg- 
raphy, and that is the construction of a vac- 
uum-tube oscillator. When the feed-back 
circuit energized by the local source contrib- 
utes more than a certain definite amount, then 
the system of circuits becomes an electrical 
oscillator, oscillating at the perfectly definite 
period which depends upon the inductance 
and the capacity of the controlling circuit. 
By varying either the inductance or the ca- 
pacity or both, we can produce any period of 
oscillation between a few periods per second 
and many millions per second, and the oscil- 
lation, once established, maintains its pitch 
indefinitely. 

"It is a generator of electrical oscillations, 
maintaining its pitch with a degree of ac- 
curacy never before obtained by any appara- 
tus constructed by man. 

"The importance of the feed-back circuit 



AMATEUR RADIO 91 

in the reception of wireless electrical oscil- 
lator, not only in wireless telegraphy but also 
in wire telegraphy and other departments of 
applied electricity, cannot be over estimated. 

"It is admitted by those skilled in the wire- 
less art that the ordinary electro-magnetic 
generator of high power will before long be 
superseded by the vacuum-tube oscillator, 
which also w r ill bring about more or less re- 
construction of wireless transmitting stations. 

"It goes without saying that long distance 
radio communication and radio phone broad- 
casting would be impossible without this in- 
vention," 



CHAPTER XV 

SOME HOOK-UPS 

A Simple Long Wave Receiver — Self-Heterodyne Circuits 
— Short Wave Regenerative Receivers — A 
Hook-up Without an Aerial 

THIS is, perhaps, the best type of simple 
long wave receiver. The use of the separate 
heterodyne permits the receiver to be tuned 
exactly to the wave. The beat note is ob- 
tained by throwing the heterodyne slightly 
above or below the signal it is desired to re- 
ceive. Both circuits should be calibrated for 
easy manipulation. As this method of recep- 
tion is designed for long waves, honeycomb 
coils or other good compact inductances are 
recommended. 

Long Wave Receiver With 
Self-Heterodyne 

A most popular type of long wave receiver 
is shown in Fig. 12. The detector tube is 
made to oscillate thus producing a beat note 

92 



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Feed-Back Regenerative Circuit. 



94 AMATEUR RADIO 

when slightly off tune with the incoming sig- 
nal. Honeycomb or other good compact coils 
are recommended. 

Always vary the "B" battery when putting 
a new detector tube in the circuit as the sensi- 
tivity varies greatly with the value of the "B" 
battery. The potentiometer shown is of great 
value in obtaining the exact point. 

With a circuit of this kind and with a two 
stage audio frequency amplifier it is possible 
to copy practically all the trans-oceanic radio 
stations operating on the long waves. For 
this type of work the aerial should be as long 
as possible and may consist of a single wire. 
Best results will be obtained when the wire 
is as high as possible and above surrounding 
objects, but even low wires will give remark- 
ably good results. 

In Fig. 13 is shown a simple circuit that 
will give excellent results in this type of ap- 
paratus. It will be noticed that the use of a 
variable grid condenser is shown. While not 
absolutely necessary at times this feature is of 
great value, especially when the unit is to be 
used for detection at different wave lengths. 

An "A" battery potentiometer is shown on 
the grid circuits of the amplifier tubes. This 
feature is of very great value when clear tele- 



AMATEUR RADIO 95 

phone speech is desired as the value of nega- 
tive current, "C," on the grids determines the 
operation of the tubes. The same "B" bat- 
tery may be used for both detector and ampli- 
fier, the detector battery being tapped off at 
about 18 to 20 volts. Sixty volts is recom- 
mended for the amplifying tubes. 

Any good type of audio frequency trans- 
former may be used. As the amplification of 
this type of apparatus is quite great it is neces- 
sary to take precautions against internal oscil- 
lations, or "howling." This condition is 
brought about through a feed-back of energy 
from one tube to the other. In general, by 
placing the transformers as far apart as pos- 
sible (about six inches), and placing the cores 
of the transformer at right angles, the trouble 
will be eliminated. (Fig. 14.) 

The selectivity of this receiver is very great. 
It is suitable for continuous wave, or C.W., 
reception, with or without shields. The use 
of shields, however, is recommended. 

Receivers of this type have been con- 
structed using the same coil as grid coil and 
coupler coil. Where this type of construction 
is used it is necessary to loosen the coupling 
between the primary circuit and the grid and 
coupling coil. Wonderful results will be ob- 




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AMATEUR RADIO 97 

tained where "Litzen Draht" wire is on all 
the forms. Operation will be materially im- 
proved by keeping the leads to the vacuum 
tubes short as possible. 

This is probably the best of the short wave 
regenerative receiver connections. The cir- 
cuits must be properly designed, however, in 
order to obtain good results. The value of 
the grid circuit condenser (Condenser A) 
should not exceed .0007 mf., and best practice 
limits it to below .0005 mf . To cover an ap- 
preciable wave-length range, therefore, it is 
necessary to design the grid coil very care- 
fully. This coil may be made variable but 
it is not recommended. 

There are hook-ups and hook-ups. So 
rapid has been the development of the science 
of radio that they are almost as numerous as 
the sands of the seashore. When the time 
comes for you to decide upon the circuit you 
are going to use, it all depends upon the appa- 
ratus you have at your disposal. 

Fig. 15 shows a circuit which can be made 
up by using a small amount of relatively sim- 
ple apparatus, to be used without art aerial. 
The values of the constants of the circuits are 
the same as those used in any ordinary short- 
wave receiver with one stage of audio ampli- 




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AMATEUR RADIO 99 

fication. It is not necessary to use separate 
"A" batteries as shown. The tuning is ac- 
complished by varying L in steps and making 
fine adjustments with C. The ground em- 
ployed was the water pipe of a local heating 
system. 

Using the above circuit, the writer, located 
just outside of Asbury Park, N. J., was able 
to hear the concerts sent out by KDKA, the 
broadcasting station at East Pittsburgh, Pa. 
KDKA was using 650-watts in the antenna. 
I have also heard the high power stations of 
the East Coast and Canada with a single tube 
and without an aerial. 



CHAPTER XVI 



THE NEWEST CIRCUITS 

The Loose Coupler, the Variometer and the Vano-Coupler 
— Honeycomb Coils — The Shielding of Panels 



A LOOSE coupler is another form of tuner 
used in place of a tuning coil. It provides 
much sharper tuning because of the fact that 
the antenna and ground are not connected di- 
rectly to the rest of the receiving set. The 
outer winding on the loose coupler is called 
the primary, and the inner coil the secondary. 
The energy is transferred from the primary 
to the secondary. (See INDUCTION in Chap- 
ter 2.) The primary inductance is usually 
made variable by means of a sliding contact, 
and the secondary made variable by means of 
a rotary switch. In short, and in non-tech- 
nical language, it is with a loose coupler that 
you tune out the stations or music that you do 
not want, and tune-in the ones you desire. 

A vario-coupler is the same as a loose 

coupler except that the secondary rotates 

100 



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PANEL 




Feed-Back, or Regenerative, Hook-Up Using Three 
Honeycomb Coils. 



io2 AMATEUR RADIO 

within the primary instead of sliding in and 
out of it. The secondary has no taps on it. 

A variometer is two inductances, one ro- 
tating within the other, and both of them con- 
nected in series, or with one terminal of the 
inner one connected to one terminal of the 
outer one. The two leads left are the termi- 
nals of the variometer. This provides a con- 
tinuously variable inductance. Tuning is 
done in the same manner as with a variable 
condenser, except that you vary inductance 
rather than capacity. When we say "varying 
the inductance" we mean that we change the 
electrical length of the instrument. When 
the wire on the rotating part of the vario- 
meter is as close as possible to the stationary 
part, the inductance is lessened; when the ro- 
tating part is at right angles to the stationary 
part, then the inductance is lengthened, mak- 
ing it possible to receive shorter or longer 
waves at will. 

There is, I have found, a decided lack of 
information on short wave reception with 
honeycomb coils. Much "high volt" and 
bitter language has been expended on the coil 
with a sweet name. Inexperienced radio fans 
after buying a complete set of them have cast 
them into the discard in disgust. 



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Tuners and One-Step of Audio Frequency 

Amplification. 



104 AMATEUR RADIO 

"Capacity" between the secondary coil 
leads, more than anything else, causes dis- 
satisfaction when copying amateur stations 
and other short wave signals, such as mu- 
sic. 

Capacity may be practically ignored when 
receiving longer wave lengths, but for short 
wave reception capacity between the second- 
ary leads should be eliminated if you are keen 
about getting the very most out of your re- 
ceiver. 

Keep the secondary leads as far away from 
each other as practicable, and, if possible, at 
right angles to each other. By secondary 
leads I mean those that run from your honey- 
comb coil mounting to the grid condenser and 
B battery. 

Other points of great importance are the 
length of the leads between the grid condenser 
and the detector tube, and those between the 
secondary and the B battery. These must 
both be as short as possible. 

In tuning for long distance signals loose 
coupling is absolutely essential. If the tickler 
is set so that the bulb does not oscillate, but is 
near the oscillating point, and the primary 
coil is moved away from the secondary, the 



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106 AMATEUR RADIO 

further you move the primary the more sen- 
sitive the set becomes. 

Moving the primary away from the second- 
ary brings the set slowly to the oscillating 
point and makes it very sensitive. It also cuts 
out to a considerable degree interference from 
nearby stations. It decreases the strength of 
signals from stations within a hundred miles, 
but increases the strength of signals from sta- 
tions of from 400 to 600 miles away. Of 
course, this is assuming that you have a two- 
step amplifier and an audion detector. 

If you have only a few sets of coils there 
is no need for you to throw away more money 
on other sizes in order to enlarge your wave- 
length capacity. 

Connect a 23-plate variable condenser in 
series with your aerial, and then you can go 
below th£ wave lengths the particular coil is 
supposed to handle. Of course, in the sec- 
ondary circuit a coil that is smaller than the 
one used in the primary must be used if the 
coils are to be utilized in this manner. 

It is generally conceded by all modern radio 
experts, that a shielded panel is desirable in 
a number of respects, chief among which is 
the elimination of capacity effects from the 



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Method of Con ccting "B," or Plate Voltage Batteries. 



io8 AMATEUR RADIO 

operator's hands while manipulating the tun- 
ing controls. 

It is thought to be an expensive, or at least 
difficult mechanical job, to properly shield 
the rear of an amateur receiving set panel, 
and it is, without proper tools, when using a 
copper plate shield. 

The writer recently overcame the high cost 
and difficulty of construction of such a shield 
by a remarkably simple process, and at a cost 
of twenty cents for a panel of twelve inches 
by eighteen inches, and the results are all that 
can be expected even from a standard navy 
shield. 

The first step is to cover the rear of the 
panel with a thin coat of shellac, thinned down 
with wood alcohol. A book of aluminum 
leaf, such as used by sign painters, is then pro- 
cured at a paint store, and while the shellac 
is very "tacky" or sticky, lay the leaf on the 
panel, sheet by sheet, in such a way as to com- 
pletely cover the entire surface. It will sur- 
prise you to see what a perfect coating will 
result, the aluminum leaf lying on the panel 
like plating on metal. 

Allow the panel to set overnight and rub 
lightly the following day with a soft cloth, to 
remove all surplus aluminum. The holes are 



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ii2 AMATEUR RADIO 

then drilled in the panel and where they come 
through the leaf, it is scraped away so as not 
to form contact with any part of the circuits. 
The coating is grounded to the earth post of 
the receiver. The interior of the receiving 
cabinet may also be coated in the same way, 
making a complete metal housing about the 
receiver. Should the very highest conductiv- 
ity be desired, silver leaf may be used, but alu- 
minum is very satisfactory. 



CHAPTER XVII 

AUDIO AND RADIO FREQUENCY 
AMPLIFICATION 

Difference Between "A.F.A." and "R.F.A."— The Uses of 

Each 

It is a mistake to think that you can get 
satisfactory results from your loud speaker 
with a crystal radiophone receiver. 

Loud speakers cannot be operated well un- 
less you have an audion with one or two steps 
of audion amplification. With two steps of 
amplification signals were heard by a friend 
of mine three blocks away from his instru- 
ments with the windows shut. 

Two kinds of amplification are in common 
use at the present time — radio frequency am- 
plification and audio frequency amplification. 
With the first system the signals are amplified 
first and detected afterwards. With the sec- 
ond the signals are picked up first and then 
amplified. 

The first system has only been used exten- 

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AMATEUR RADIO 119 

sively in amateur radio work during the last 
few months. With it you can use two to six 
steps without distortion of signals or the howl- 
ing of bulbs. Faint signals can be amplified 
with this system which never would be heard 
with the audio frequency amplifiers. 

It must be remembered that with audio fre- 
quency amplifiers, if more than two steps are 
used, everything will be amplified but what 
you want. Instead of getting music you will 
get the arc light four blocks away making a 
noise like Niagara; somebody's flivver pass- 
ing down the street roaring like the Twentieth 
Century Limited ; the door bell behaving like 
a fire alarm. If you had radio frequency am- 
plifiers these undesirable noises would be prac- 
tically unamplified. 

With the radio frequency amplifiers you 
must use a different type of amplifying trans- 
former, and the method of connecting up the 
amplifier circuit is of quite another kind than 
that used when operating an audion frequency 
amplifier. Your dealer will explain to you 
the differences if you should decide to install 
the more efficient kind. 

Radio frequency amplification, as you see, 
offers unusual advantages in receiving radio 
signals of all types, especially radiophone or 



i20 AMATEUR RADIO 

modulated waves, over all other known meth- 
ods of receiving. The use of audio amplifica- 
tion is familiar to operators, and is known to 
be limited. A signal which is too weak to op- 
erate the detector tube can never be amplified 
by audio amplification, regardless of the num- 
ber of stages used. After the signal is strong 
enough to operate the detector, audio ampli- 
fication is effective up to two stages. Audio 
amplification, beyond this, is limited by dis- 
tortion and inherent audio tube noises. 

By radio amplification the original weak in- 
coming signal is raised to a value for effective 
operation of the detector tube. Regardless of 
how weak the signal is to start with, a proper 
radio amplification will bring it up to suffi- 
cient strength to make the detector function, 
after which audio amplification may be ap- 
plied. Stations which are normally beyond 
range can, therefore, easily be brought in by 
using radio amplification. 

By using a correct radio transformer the 
incoming signal frequency is amplified with- 
out the accompanying tube noises and local 
sounds, since the transformer will not respond 
to low frequency or audio sounds. Jarring 



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AMATEUR RADIO 



the tubes, etc., will, therefore, not produce a 
ringing sound or disturb the receiver in any 
way, as with audio, nor limit the number of 
stages or radio amplification which the op- 
erator desires to use. 



CHAPTER XVIII 



CONDENSERS 



How Condensers Assist in Tuning — Fixed and Variable 

Condensers 



Condensers are very important parts of a 
receiving set. Without them we could not 
tune sharply. Condensers in their simplest 
forms or the kind used in practically all small 
amateur receiving sets consist of a series of 
wax paper sheets coated on one side with tin 
foil. These sheets are laid club sandwich- 
wise, a sheet of tin foil, a sheet of wax paper 
and then a sheet of tin foil again until there 
are, say a layer of seven pieces of paper and 
six of tin foil. Half the sheets of tin foil are 
connected to one wire and the other half 
to another wire, these two wires forming the 
terminals of the condenser. 

Condensers have the property of accumulat- 
ing electrical energy and suddenly discharg- 
ing it and while very essential they are usu- 
ally overlooked and unknown to some radio- 

123 




PAPER 

FOIL 

PAPER 

FOIL 

PAPER 

FOIL 

PAPER 



CONNECTION 

CONNECTION 
Diagram Showing Construction of Fixed Condenser. 




Variable Condenser. 



AMATEUR RADIO 125 

phone fans, as they are usually hidden away 
in the back of the receiving set in an incon- 
spicuous place. 

Another form of receiving condenser con- 
sists of a number of half circular plates so 
placed that they may be rotated or moved past 
a series of fixed semi-circular plates. The 
plates do not touch as the space between them 
takes the place of the paraffin paper in the 
previously mentioned type. 

The rotating semi-circular plates are 
mounted on a shaft and attached to a knob so 
that the condenser may be adjusted at will to 
any capacity desired. 

Variable condensers are capable of being 
adjusted more finely than regular tuning coils 
or loose couplers for the changes brought 
about by varying the positions of the plates are 
very gradual. In a tuning coil or loose 
coupler the tuning must naturally be very 
rough. 

Experimental radio receiving sets require 
condensers whose quality is high and whose 
price is reasonable. It is easy to manufac- 
ture low-priced condensers as is evidenced by 
the large number now available. It is more 
difficult, however, to construct a condenser 
which is electrically and mechanically good, 



126 AMATEUR RADIO 

and yet at the same time keep the cost of 
construction low. 

The value of a good condenser in a receiv- 
ing set is not always fully appreciated. The 
dielectric losses of the condenser are equiv- 
alent to adding a series resistance in the oscil- 
lating circuit. To add a series resistance in 
the oscillating circuit means loss of energy 
which, in turn, means broad tuning and di- 
minished signal strength. It is thus impor- 
tant that the dielectric losses in condensers be 
kept low. 



CHAPTER XIX 



TUNING AND INTERFERENCE 

Proper Method of Operation of Audion Set — How to 
Avoid Interference, or Q.R.M. — Way to Find the De- 
sired Wave-Length — Meaning of Resonance 
Between Transmitter and Receiver 



QUITE a few amateurs are puzzled after 
they have installed their sets as to how they 
should tune-in for desired signals. They find 
that, try as they may to get the music, they 
succeed in getting nothing but cryptic and 
otherwise, to them, unintelligible sounds from 
the big commercial spark stations. 

I've often heard people who had just in- 
stalled perhaps a $150 set exclaim: 

"Whatever you do don't buy one of these 
sets. I've fooled with it for two hours or 
more and can't get anything but faint signals." 

Read the following closely and you will 
never be troubled in this way. To tune a re- 
ceiving set that incorporates a loose coupler 
as the main tuning device set the coupling as 

tight as you can possibly get it, tune in the de- 

127 



128 AMATEUR RADIO 

sired signals with the primary or outside in- 
ductance, and then tune in with the secondary 
or inner inductance until you have the great- 
est strength of signals. 

Loosen the coupling between the primary 
and the secondary until the signals are just 
audible. Retune with the primary and the 
secondary until the signals are the strongest 
at the present setting of the coupling. Finally 
tighten the coupling until you get the max- 
imum clarity. This method of tuning with 
the loose coupler is the only right way, and 
when the signal is tuned in in this manner 
there will be a minimum of interference, or 
"Q.R.M." 

With a regenerative receiver, having a 
vario-coupler, plate variometer and grid 
variometer the proper method of tuning in de- 
sired signals is as follows: 

First set the coupling of the vario-coupler 
at maximum degree, or, in other words, the 
primary and secondary are as near together as 
possible. Tune with the switch knob on both 
the primary and secondary, then tune with the 
grid variometer until the greatest signal 
strength is obtained. The plate variometer, 
which should have been set at zero, while tun- 
ing the primary and secondary of the vario- 



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coupler and the grid variometer, is now 
moved slowly until you get greatest signal 
strength without distortion. 

If you desire to tune in radiotelephone 
music you should set the plate variometer well 
past the oscillating point. Then tune with the 
vario-coupler to the wave-length the music is 
being transmitted on. 

The grid variometer is varied slowly until 
a loud "squeal" is heard in the phones. You 
will notice that this squeal starts at a very high 
frequency, and as you continue to turn the 
knob it slows down until it reaches an inau- 
dible point, then increases in frequency again 
to the point where it is inaudible, or above 
10,000 cycles. 

At the point where no sound is heard be- 
tween the two howls is the spot you should 
hear the music or voice, and if by any chance 
you do not hear anything wak a minute or two 
before you commence tuning again, for the 
station may not be talking at the moment. 

The coupling between the primary and the 
secondary of the vario-coupler is preferably 
left at maximum ; as in most sets, the coupling 
does not make very much difference. Try it 
out and see what it does on your set. 

All this may sound complicated and "deep 



AMATEUR RADIO 13 1 

stuff" to the novice, but after a trial or two 
you will see how easy it is. Always remem- 
ber to tune with the grid-variometer first, then 
regenerate the signals with the plate vario- 
meter. Be sure to have your auction lighted 
brightly enough to enable it to oscillate. 

Tuning of the receiving to the beginner is 
a thing that has a lot of mystery connected 
with it The question has been asked, "How 
do you know where to pick up the desired 
signal?" There is no way to tell on a set that 
the amateur is not familiar with. But, after 
the set has been in operation for a little while, 
the beginner will soon learn exactly where to 
pick up the desired signals. 

Most sets have dials on them that are di- 
vided off into 180 degrees with the numbers 
engraved on them for every ten degrees. 
These numbers have nothing whatsoever to 
do with the wave-length of the station, but are 
simply put there to enable the operator to re- 
member easily at what point a station will be 
heard. Usually the lower numbers represent 
the short wave lengths and as the dial is turned 
about the longer waves will be heard. 

With most sets it is a very simple matter to 
soon learn exactly where the desired signal 
may be heard, and the set may be left in the 









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AMATEUR RADIO 133 

same setting all the time if it is used just for 
receiving the broadcasting. In other words, 
the set is tuned to receive the music from your 
pet broadcasting station and there is no neces- 
sity to move the knobs again unless other sta- 
tions are wanted. 

The theory of tuning is a long and com- 
plicated study, and a few words on the subject 
may clear up a lot of misinformation. In the 
first place, every transmitting station has a 
certain wave-length upon which the trans- 
mitted signals or voice is transmitted. The 
receiving set, however, is capable of receiving 
several wave-lengths by tuning the knobs 
about. A transmitter can also be made to 
transmit on several wave-lengths, but cannot 
be tuned as fast as receiver. 

When your receiving set is tuned to receive 
a certain transmitting set it is in resonance 
with the other station. A simple way to ex- 
plain this is to say that the wave lengths are 
very nearly the same. This is accomplished 
by adding or subtracting a certain number of 
turns of wire in the coils and thus equalizing 
the wave-lengths of the two stations. By the 
addition of different pieces of apparatus it is 
possible to make this tuning very sharp, and 
there are some sets that will receive the de- 



AMATEUR RADIO 135 

sired signals only. However, these sets are 
very expensive and the operator has to be an 
expert. The average amateur set will not 
tune sharp and a great deal of trouble has been 
caused by some beginners filing complaints 
about some amateur spark transmitter. Usu- 
ally the spark transmitter is tuned to a sharp 
wave and is operating legally, while the be- 
ginner's set is the one that is at fault, as it is 
incapable of sharp tuning. If more beginners 
would study up on these facts before purchas- 
ing a set there would not be so much inter- 
ference. Many amateurs have home-made 
receiving sets with which it is possible to sit 
and listen to their favorite programs all the 
evening without hearing a single interfering 
station. 

Of course there are certain cases where it 
is impossible to tune out the unwanted station 
with any set. Some amateurs are unfortunate 
enough to be located very near one of the 
naval or ship stations, and it is impossible to 
do any tuning, owing to the close proximity 
of the transmitter. When buying a set ask 
for a demonstration showing the selectivity of 
the set, as by doing this the beginner will save 
himself a great deal of trouble in the future. 



CHAPTER XX 

A PERSONAL EXPERIENCE 

How a First Step of Amplification Acted as a Detector, 

. and the Second Step as a One-Step Amplifier and 

Oscillator— Visiting the "Other Fellow's" Station 

Let me here refer to a personal experience. 
While enjoying the music on a friend's new 
receiving set with a two-step amplifier, one 
evening, I noticed when I turned the detector 
tube out and left the two steps of amplifica- 
tion burning, that strong continuous wave sig- 
nals still came in. 

After keeping my ears glued to the phones 
for about fifteen minutes, during which time 
I heard some of the best sending I had ever 
listened to, to my surprise the station signed 
"WSO." This is the Radio Corporation of 
America's station at Chatham, Mass., which 
was working Stavanger, Norway, whose call 
is LCM! The amateur station I was visiting 
is at Asbury Park, N. J. 

The receiving set was a short wave one, and 
no adjustment that I made seemed to change 

136 



AMATEUR RADIO 137 

the strength of the signals, except when I 
turned the filaments lower or brighter on the 
two-step. The first step of amplification was 
working as a detector, and the second step of 
amplification as a one-step. 

So I then connected the antenna and ground 
to the primary of the amplifying transformer 
of the first step, and many long distance sta- 
tions came in, including NSS, NBA, NAT, 
NAU and BZR which are, respectively, 
Annapolis, Darien, (Panama), New Orleans, 
San Juan, (Porto Rico) and Bermuda. Need- 
ing a way to tune, I connected a variable con- 
denser in series with the antenna which en- 
abled me to tune NSS entirely out and tune 
NAT in. 

Another thing I noticed was that when the 
filament current of either tube was increased 
or decreased, some of the stations would come 
in louder than others, and tuning could be 
done with the filaments of the tubes. 

All the time that I was copying these sta- 
tions there was a high pitched whistling in 
the telephones, probably due to the close prox- 
imity of the amplifying transformers. 



To the real radio enthusiast the other fel- 
low's station is always a source of interest. 



138 AMATEUR RADIO 

This is not surprising when one considers 
the number of possible variations in the ar- 
rangement of the essential apparatus, to say 
nothing of the numerous original devices be- 
loved of the amateur. 

Apart from those whose interest is transi- 
tory, and who have nothing more than a radio- 
phone receiver which they have acquired 
simply because they think it is the thing to 
possess one; and apart from those who buy 
expensive self-contained sets in the fond but 
seldom realized hope that without any skill 
on their part they will be able to delight their 
friends with wireless music, via loud speaker 
(with only a frame aerial about as large as 
an electric toaster) one may divide radio am- 
ateurs into two classes — experimentalists and 
operators. 

In the first class we have those whose chief 
delight is in designing and making some new 
piece of apparatus or re-arranging existing ap- 
paratus with a view to greater effectiveness. 
In many cases they cannot even read the code. 
But, incidentally, you may have noticed that 
this does not prevent them from talking glibly 
of the Eiffel Tower or Honolulu, as though 
they were old pals. 



AMATEUR RADIO 139 

The other class consists of those whose chief 
delight is to intercept messages, and who judge 
of the efficiency of their station not by the 
noise it makes when, say the music starts up 
but by the long distance traffic it enables them 
to copy. 

Of course, there are many in this class who 
do their share of experimenting also; but as 
this is principally to improve the receiving 
range, it does not affect the classification. 

A glimpse at the other fellow's station is 
generally sufficient to enable one to say to 
which class he belongs. The experimental- 
ist's set is never finished, invariably looks like 
a junk heap, and needs a lot of persuasion be- 
fore it can be coaxed into articulation. 

It never is doing as well when you happen 
to be there as it did last Wednesday week 
when, 

"Gee, you should have heard the signals the 
other night when 'Loose-Coupler Abe' was 
here. They nearly broke your ear drums two 
blocks away." 

The storage battery is run down, or perhaps 
the slider on the inductance has sprung a leak. 
There's never any lack of excuses for its 
backsliding. 



;i 4 o AMATEUR RADIO 

On the other hand, the keen operator, main- 
tains his set at concert pitch seven days a week, 
ready at all times to respond to any of the old 
favorites whose tuning adjustments he knows 
to a degree. 



CHAPTER XXI 



STORAGE BATTERIES 

Accumulators Necessary for Radio Receivers — How Bat- 
teries are Rated — Testing and Charging Batteries 



It is impossible to properly light a vacuum 
tube detector or amplifier unless a storage bat- 
tery is used. Dry cells are no good for the 
purpose. 

The reason is that the average vacuum tube 
draws about one ampere per hour, and with 
such a strain on it a dry cell will last but a 
short time, when it will have to be replaced. 
With the price of these cells at their present 
high level it is poor economy to do this, as 
you will have to buy a new set of six cells 
about every week if the receiving set is used 
very much. The storage battery, on the other 
hand, has a much longer life, and when it be- 
comes low it may easily be charged up again 
at almost any garage. 

In order that you may understand some- 
thing about a battery before you buy it it will 

141 



142 AMATEUR RADIO 

be well to remember that storage batteries are 
rated by the number of volts that they will 
give and the number of ampere hours the bat- 
tery will be able to deliver this voltage. You 
will find that there are many different kinds 
of ratings on storage batteries. These ratings 
are given in ampere hours, and run from 10 
ampere hours upward. The thing that is de- 
sirable is to have this rating as high as pos- 
sible, as the whole meaning of the term is that 
the battery will deliver one ampere for so 
many hours, hence the saying, "this cell has 
sixty ampere hours." When you hear that 
you will know that that particular battery will 
give one ampere continuously for sixty hours. 
When you use this battery with a vacuum 
tube that draws one ampere it will light the 
filament for about sixty hours. Now, suppose 
you put on one step of amplification, or an- 
other bulb. This bulb will also draw one am- 
pere, making a total of two amperes that are 
drawn from the battery. This will exactly 
halve the number of hours the storage battery 
will last before it has to be recharged, or only 
thirty hours. The addition of another am- 
plifier will cut it still lower, as you will draw 
three amperes from the battery. This will 
leave you only twenty hours of life from a 



AMATEUR RADIO 143 

storage battery that will give sixty ampere 
hours. As you will never use the battery for 
the full sixty or twenty hours continuously it 
will really last longer, as the battery has a ten- 
dency to recuperate during the time that it is 
not in use. Of course it w T ill never come back 
to full capacity, but there will be a slight rise. 
Never let the battery get fully discharged or 
even low, because it is bad for it, and, in time, 
will ruin it entirely. 

There are many ways of testing batteries 
and among them you will hear of the trick of 
snapping a piece of wire across the terminals. 
There is nothing that will ruin a battery 
quicker than this. Another way is to connect 
a voltmeter across the lugs. A cell of the bat- 
tery may become nearly exhausted, yet it will 
show its full voltage with this method and it 
is absolutely useless. A small ammeter will 
"go up in smoke" if you try using one, so don't 
do that. The only sure way to test a storage 
battery is to get a hydrometer. 

A storage battery may be ruined by having 
an overcharge as well as being allowed to 
stand discharged. They must be taken care 
of if you want them to last. For radio work 
a battery should not have over six volts and 
the easiest way to tell this is to look at the 



144 AMATEUR RADIO 

number of little vent caps on the top. Each 
of these caps takes care of one cell and each 
cell is good for two volts. 

Here are some tips on rectifiers for charg- 
ing storage batteries : The lamp used for the 
charger should be a carbon lamp and the more 
lamps added the higher the amperage will be 
that is passed. This will make the battery 
charge up quicker, but the rate should not be 
over five amperes. If the battery is charged 
too fast it is apt to spoil the plates. 

The plates do not have to be formed but 
once, before the first charge, but every time 
new aluminum plates are put in they will have 
to be reformed. The rectifier will work well 
if enough amperage is passed and the lights 
are added to make the amperage high. If it 
is too low the battery will not charge up prop- 
erly. The rectifier cannot be used to light the 
filaments direct, and the amateur is advised 
not to do this as it will surely burn them out. 
The rectifiers will run warm in time and more 
water will have to be added as it evaporates. 
Do not add any more borax. 

If the rectifiers boil and get too hot it is a 
sign that too much amperage is being passed 
or that it is not connected up correctly. The 
whole secret of charging the battery is to have 



AMATEUR RADIO 145 

the charging rate correct, and to do this it is 
necessary to experiment as some batteries re- 
quire a higher rate than others. The length 
of time required to charge a battery is also 
dependent on the number of amperes that are 
being passed, that is the lower the amperage 
the longer the charge will take. Do not think 
that the battery can be charged up in three 
or four hours, because this cannot be done. It 
will require at least twenty-four hours, if the 
battery is all the way discharged. By getting 
a hydrometer a sure method of testing the bat- 
tery can easily be accomplished. Full direc- 
tions come with every instrument 



RADIO GLOSSARY 

A.C. — Alternating Current. 

Ampere — The practical unit of electric cur- 
rent strength ; such a current as would be given 
with an electromotive force of one volt 
through a wire having a resistance of one ohm. 

Aerial — The wires suspended on the roof of 
a building that are used for receiving or trans- 
mitting. A single wire aerial is all that is 
needed for receiving. 

Antenna — This term means the whole 
aerial and ground system. 

B Battery — A small dry battery that is used 
in a vacuum tube circuit only. It is built so 
that a high voltage is given which is necessary 
for the operation of the tube. Some of the 
batteries are arranged in such a way that the 
voltage may be varied. 

Current — The amount of electricity passing 
a given point in unit time, measured in 
amperes. 

G.W. — Continuous Wave. 

D.C. — Direct Current. 

146 



AMATEUR RADIO 147 

Detector — The device, either crystal or 
vacuum tube, that is used to detect the incom- 
ing waves and rectify them so that they may 
be made understandable. 

Electromotive Force (E.M.F.) — The term 
applied to electric pressure, measured in volts. 

Grid — A zinc plate in a storage battery or 
a lead plate for retaining the active material 
in a storage battery, or a zig-zag coil of wire, 
between the plate and filament in an audion 
tube. 

Ground — The opposite end of the aerial 
circuit. It usually consists of a wire connect- 
ed to the cold-water pipe. It is also used for 
connecting the lighting arrester to. If used 
for the latter purpose it should be an outdoor 
ground and many consist of a pipe driven deep 
into the ground or any buried metal. 

Honeycomb Coils — A type of coil that may 
be plugged into a special fitting. Different 
sized coils are used for different wave lengths. 
Duo lateral coils are about the same thinr?. 
Both are very efficient for long wave re- 
ception. 

Induction — The process by which a mag- 
netizable body becomes itself electrified in the 
presence of an electrically charged body or a 
magnetic field electrically produced. 



i 4 8 AMATEUR RADIO 

Loop Aerial — A form of indoor aerial and 
direction finder. Usually wound on a form 
about five feet in diameter. Cannot be used 
with a crystal detector and works best only 
with several stages of amplification. Not as 
efficient as the outside aerial and not recom- 
mended for the beginner. 

Loose Coupler — A form of tuning coil that 
is a little more efficient than the plain tuning 
coil. It enables the operator to "loosely cou- 
ple" the set and thereby eliminate a lot of in- 
terference. 

Loading Coil — A large single slide tuning 
coil that is used to load a receiving set up to 
longer wave lengths. Not a very efficient 
form of tuning. 

Microphone — An instrument for magnify- 
ing faint sounds by the variation in electrical 
resistance caused by variation of pressure at a 
loose coatact. 

Oscillation — A high-frequency electric cur- 
rent, the maximum value of which con- 
stantly diminishes, with a speed depending on 
the damping effect present. Frequently 
linked in radio theory w T ith the Herzian 
Waves, the basic radio conception, which 
deals with the wave propagation of electro- 



AMATEUR RADIO 149 

magnetic induction, the underlying principle, 
of course, of wireless communication. 

Ohm — The unit of electrical resistance; 
concretely represented by the resistance of 
400 feet of common iron telegraph wire. 

Rheostat — An instrument by which a vari- 
able or adjustable resistance may be intro- 
duced into a circuit to regulate the strength 
of the current. 

Resistance — The opposition to the flow of 
current shown by every direct current (D.C.) 
circuit, measured in ohms. 

Spider Web Coils — A form of tuning coil 
wound similar to a spider web. They are 
also called stagger wound inductances. Very 
efficient for a regenerative set. 

Tuning Coil — Usually either a double slide 
or triple slide. The difference in efficiency 
is very small. A cylindrical coil of wire upon 
which a sliding contact is made with the aid 
of a special slider. This varies the wave- 
length of the set and tunes it to the incoming 
signal. 

U.D. — Undamped, or Continuous Wave. 

Vacuum Tube or Audion Bulb — A form of 
detector making use of the electronic theory. 
Most efficient form of detector. Certain 



150 AMATEUR RADIO 

forms of the tube may be used for amplifiers 
and others for transmission. This type of 
tube used exclusively for transmission of 
speech and music. 

Variometer — Will help to tune the set using 
a variocoupler. Also may be connected into 
the circuit of a crystal detector that will give 
good results. 

Variocoupler — Still another form of tuning 
unit. It will tune about the same as a loose 
coupler. Very efficient in a set using a vac 
uum tube if connected in with two vari- 
ometers. 

Volt — The practical unit of electromotive 
force; such a force as would carry one ampere 
of current against one ohm of resistance. 

Variable Condenser— The instrument that 
consists of a series of aluminum plates, half 
of which are stationary and the other half 
movable. It is used to vary the capacity of 
the set and will greatly help the tuning. 

Wave Length — The distance between the 
crests of each ware or series of wave trains 
measured usually in meters. 

Wave Train Frequency — The number of 
wave trains or groups of wave trains radiated 
per second by transmitter antenna. 



AMATEUR RADIO 151 

Watts — The units by which power is meas- 
ured. In D.C. Circuits the voltage multi- 
plied by the amperes flowing in the circuit 
gives watts. A watt is equal to 1-746 horse- 
power. 



ARLINGTON WEATHER REPORT. 2,500 

Meters, Call Letters, N. A. A. 

Sample Report: QSTdeNAA, USWB, S01081— T02261 
DB 0251— H 00844— G 01261— K 00441— P 01242 



QST— General call. 

de — From 
NAA — Arlington Station 
USWB— U. S. Weather 
Bureau 



010"— 30.10 inches, 
Barometer 
"8"— Direction of wind 
"1"— Velocity of wind 




Direction of Wind 
r. rx , ^ ^ ^ ^ — O Calm 

Du — Duluth G — Green Bay 

D — Detroit M — Marquette N 

Ch — Chicago V — Cleveland NW /^ • 

U— S. S. Marie L— Alpena A> 

F— Buffalo 

K-Key West, Fla. 

S— Sidney, Nova Scotia. Wl ' 

T— Nantucket, R. I. 

DB — Delaware Breakwater. Sw\C 

H— Cape Hatteras, N. C. ~ ^^5 

C— Charleston, S. C. $ 

P — Pensacola, Fla. t-* . #» ,. . 

^ D , Report is for conditions 

13— Bermuda. at 8 P M> of the day sent 

out from Arlington. It is 

_ ======= ___ sent out 10 P. M. 

Beauford Wind Intensity Scale 

Statute M.P.H. 

Calm 0—3 

1 Light Air 8 

2 Light Breezes 13 

3 Gentle Breezes 18 

4 Moderate Breezes 23 

5 Fresh Breezes 28 

6 Strong Breezes 34 

7 Moderate Gale .40 

8 Fresh Gale 48 

9 Strong Gale 56 

10 Whole Gale . .- 65 

1 1 Storm 75 

12 Hurricane 90 

Statute Miles per Hr:— 1.15. Nautical— M. P. H. 






ARLINGTON— TIME SIGNAL— 
2500 METERS 

Note. The Arlington Station sends time sig- 
nals on a wave length of 2500 meters commenc- 
ing at 11 :55 A. M. and 9:55 P. M. every day. 
Final signals at 12 Noon and 10 P. M. are for 
the meridian of 75 degrees west of Greenwich. 
Every tick of the standard clock at the Naval 
Observatory, Washington, is transmitted as a 
dot, omitting the 29th second of each minute, the 
last five seconds of each of the first four min- 
utes and finally the last ten seconds of the last 
minute. The 12 Noon and 10 P. M. signal is 
dash. 



SJfFM to* zo JO* /&• fO~ SB 4 

SG 
••MM«M*M*MltMn«t9»N«O«MI0«MNM«H«l8MIM«l0000O 

J* 

ioP/rt M _ 

«£0000 JO!* £L Qm 



U. S. RADIO LAWS AND 
REGULATIONS 

The owner of any amateur radio transmit- 
ting station must obtain a station license be- 
fore it can be operated. These regulations 
cover the operation of radio-telephone stations 
as well as radio-telegraph stations. 

Station licenses can be issued only to citizens 
of the United States, its territories and 
dependencies. 

Transmitting stations must be operated 
under the supervision of a person holding an 
Operator s License and the party in whose 
name the station is licensed is responsible for 
its activities. 

The Government licenses granted for am- 
ateur stations are divided into three classes as 
f ollows : 

Special Amateur Stations known as the 
"Z" class of stations are usually permitted to 
transmit on wave lengths up to approximately 
375 meters. 

154 



Department of Commerce 

MACK) senvict 



INTERNATIONAL MORSE CODE AND CONVENTIONAL SIGNALS 

to M vss» rom *ti onun muc inner bacho comml-nxutkn 



L A dash to cq«kl » thtee dots. 3. The space be< ween (wo letter* Is eqoal U tVee d*4a 
2. Tbe space between parts of lie unf fetfe* i« equal to o*e dot. 4. The cpaee between lit words ts t*\**l to **e dots. 


Asasa 


Perm) _ 




B SOB • • • 






Caatn* 


Semicoma. 




D«M 






Es 


Coama.... - .. 


• aaa 1 • sssi • saas 




<>loa ^ 


■■b mta na • • s 


Ha ••• 


Initmfailm . *.«- , , 




I • • 


IUeJaaMEUe-s psiii 




L • SBBS • • 


Asastrsahe 


aa.aaaas.asaa 


MsflM 


Hjtkea «... ........... 


aaa a a s • aaa 


N.* 






n i_ MSB a^y 


Rar isdkatatf; frartiea 




Psaasaaaa 


Pareatheasa 

• 




Beaoaa 


lai'trtf4 rtaaan 




8*99 


Uaekrfiae » *.. 


• a aaa sasa a aas 


!«*«■ 


T>«ahi> dsak 


aaa a -s ef aas 


-?*#•« 






«-•«■«■ 


Distress Cal *.„ 




Iat««« 






Yaaaaaaaaaa 


Attests** call to areeede every traastnissioa. 


aaaaaaaaaas 


Z aaa aas • • 






A (German^ 
£MlQ0Vkmmm% 

SK?M • CSV 

CH ^German -Spanish) 

•CiFretxU 

JlCgpanWiy 

D (Germari) 

V (German) 
, saaasaas 


Fran (•>)... .*» .~ .. 

Iirrtatiao to Jrusaut (fs ahead) 

WsraJat-sifk aswsr , 


^aaavas ■aaaasaass 

aas mm 9 

aaa a aaa 

aaa aas • « aas saj 


Qaeatiaa (atoaae reseat after )— farter 




WsM 




Break (Bfc) (atosMe sask) , 

Yuiummi 


aaa a a a aas 










i • • • wm oar 


ftrsr ., 


a • •»•••• 


4 • • • a aaa 


Baeehrea) (O.E.)..., - - 


a aas a 


«• aaasesa 


Fsattsa teasel (to precede all assittos rues- 






Bad of sack simige (crass) 




0_«_ 


Trsiisaal arias tniahed (end of work) (eene.o 
sion af eomspeodesee) 


• ••_••» 



156 AMATEUR RADIO 

General Amateur Stations which are per- 
mitted to use a power input of 1 kilowatt and 
which cannot use a wave length in excess of 
200 meters. 

Restricted Amateur Stations are those lo- 
cated within five nautical miles of Naval radio 
stations, and are restricted to y 2 kilowatt in- 
put. These stations also cannot transmit on 
wave lengths in excess of 200 meters. 

Experimental stations, known as the "X" 
class, and school and university radio stations, 
known as the "Y" class, are usually allowed 
greater power and also allowed the use of 
longer wave lengths at the discretion of the 
Department of Commerce. 

All stations are required to use the mini- 
mum amount of power necessary to carry on 
successful communication. This means that 
while an amateur station is permitted to use, 
when the circumstances require, an input of 
1 kilowatt, this input should be reduced or 
other m^ans provided for lowering the an- 
tenna energy when communicating with near- 
by stations in which case full power is not 
required. 

Malicious or wilful interference on the part 
of any radio station, or the transmission of any 
false or fraudulent distress signal or call is 



AMATEUR RADIO 157 

prohibited. Severe penalties are provided 
for violation of these provisions. 

Special amateur stations may be licensed at 
the discretion of the Secretary of Commerce 
to use a longer wave length and higher power 
than general amateur stations. Applicants 
for special amateur station licenses must have 
had two years' experience in commercial radio 
communication. A special license will then 
be granted by the Secretary of Commerce only 
if some substantial benefit to the science of 
radio communication or to commerce seems 
probable. Special amateur station licenses 
are not issued where individual amusement is 
the chief reason for which the application is 
made. Special amateur stations located on or 
near the sea coast must be operated by a per- 
son holding a commercial license. Amateur 
station licenses are issued to clubs if they are 
incorporated, or if any member holding an 
amateur operator's license will accept the re- 
sponsibility for the operation of the apparatus. 

Applications for operator's and station li- 
censes of all classes should be addressed to the 
Radio Inspector of the district in which the 
applicant or station is located. Radio In- 
spectors' offices are located at the following 
places: 






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158 AMATEUR RADIO 

First District Boston, Mass. 

Second District New York City 

Third District ... . Baltimore, Md. 

Fourth District . . . Norfolk, Va. 

Fifth District New Orleans, La. 

Sixth District San Francisco, Cal. 

Seventh District Seattle, Wash. 

Eighth District Detroit, Mich. 

Ninth District Chicago, 111. 

Tenth District (Alaska) . .Seattle, Wash. 

No license is required for the operation of 
a receiving station, but all persons are required 
by law to maintain secrecy in regard to any 
messages which may be overheard. 

There is no fee or charge for either an 
operator's license or a station license. 




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Connecticut 

Libraries 



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